| dracul |
After trying everything I could think of I keep ending up with an image on the wall that is round and small with the round area being bright and the rest dark.
I have 2 fresnel lenses that are split from Diylabs. I have a transparency with text at image plane and I have a 13 inch lens triplet for a projection lens.
I got a lamp-----fresnels together(9 inches from lamp)-----transparent image(2 inches away)-----lens triplet(13 inches away)
At this point I just want to have a OHP type setup where the fresnels are as one. I figured I had the fresnels oriented wrong so I tried: 1: grooves facing out
2: grooves facing in( i thought this was correct)
3: grooves facing the lamp
4: grooves facing the image plane
Add to this combination and I also tried putting the longer FL fresnel closest to the lamp.
Doesnt Work. Doesnt Work.
The problem seems to be at the image plane. The light hitting it is not even from side to side top to bottom.
Somebody please help me. I have no idea what the hell is going on. Is it possible I have the wrong frensnels sent to me? |
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| jcbklyny |
It sounds like your focal lengths are off. What lamp are you using? and how is everything spaced out? are you using your own case or regular OHP?
And the grooves should be facing towards each other for the fresnels. |
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| Elkaid |
I faced exactly the same problem.
I simply had to adjust the distance between my first fresnel from the lamp. (In my case, I had to reduce the distance)
I hope this helps ! |
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| ace3000_1 |
i had this problem in mine too belive it or not, i cut my frensel down it changed the focal to double lol so i got one out of my infocus projector and now it works spot on except my infocus frensel is a tad small but it proves that i need another frensel to shorten my focal, it sounds to me dracul that your focals are way out , just like mine was, id be fooling with the distance from the lamp to the frensel if i was u cos its definatley a focal problem in that area.
Trev |
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| Hezz |
It's possible that you've got the fresnels reversed or they were mislabeled. If you have the split fresnels it's possible you got two of the same focal length by mistake.
Put the single (split) fresnels up to your regular computer monitor about 3-4 inches away and look at the image. They should have different degrees of magnification and the shorter focal length one will give a bigger but poorer picture.
Hezz |
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| dracul |
| quote: | | it's possible you got two of the same focal length by mistake. |
Nope, one throws a larger image.
fresnels before the image plane does not work unless my fresnels are larger I think so I gave up on this and tried the image plane between the fresnels.
This worked except now I cant seem to get a sharp image from left to right and top to bottom. Its only sharp in the center. Is this because my fresnels are bowing? Do I need to sandwitch both between glass? They dont look bowing much to my eye. How critical is this?
Also the second fresnel had to be around 4 inches from the image plane in order to project the entire image. 2 inches did not cut it. not sure why. So yeah now I have 9 inches to Fresnel1 2 inches further is the image transparency than 4 inches further is fresnel 2.
| quote: | | i cut my frensel down it changed the focal to double lol so i got one out of my infocus projector and now it works spot on except my infocus frensel is a tad small but it proves that i need another frensel to shorten my focal |
Cut them down how to what size? you mean evenly from all sides inwards? Dont I need larger fresnels not smaller?
If I still want fresnels before the lcd what size fresnel do you think I would need for a 15 inch lcd?
What I noticed with both fresnels before the lcd was the light circle was not large enogh to cover the lcd plane. Especially fresnels sandwitched together as come sold. So I dont understand why diylabs recomends this method. It does not work with 15 inch lcd. Maybe with a 8 inch. |
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| ace3000_1 |
| quote: | | Cut them down how to what size? you mean evenly from all sides inwards? Dont I need larger fresnels not smaller? |
heya dracul, yeah if u have read my thread u would have seen what lcd im using, im using a 7inch wide screen lcd, its alot smaller then a 15inch lol thats why i cut mine down and its cut evenly from all sides to the center, the frensel is cut to the overal size of the lcd not just the lcd its self so its alittle bigger then the lcd, your saying your light beam isnt wide enough to cover your lcd area, are u using a condenser lens by chance? or a reflector? there is somthing definatley going on there dracul it could be any one of the things that have been mentioned in the posts above, get some cardboard and place it vertical from your light source to where your frensel is, u will see the light beam on the cardboard and see how wide it actually is, also get your 9inch focal frensel and take it out and put it under the light, focus it so u get a point of light on the table, that will be the focal of that frensel, if your frensel has been cut into the rings then your focal is out on that frensel, ive learnt that buy cutting the frensel down into the rings part it will alter the frensels focal cos your actually changing the shape of or pitch of the lens, u will get a longer focal because the rings pitch has changed at the sides , they wont collimate light unless u use 2 of them to half that focal for the given focal size that was of the original. You told us that diylabs cut yours for u, if he has cut into the rings even just 10mm will alter the focal alot and if thats so then your focal could be even 12inches now not 9.
Trev |
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| dracul |
Ace it doesn t look like the fresnels are cut on the sides all the missing corners are equal on all 4 sides of each fresnel.
I have gotten a much better image now and I can project the entire image plane but it is still soft on the sides. Throughout the this tweaking process I realized soft areas are a result of less light . So I got the light more even now and therefore focus more even but it is still soft on the sides like I said.
Here is my setup:
1: lamp
2: 9 inch space
3: 13 inch FL Frensel(groves facing LCD)
3: 2 inch space
4: Lcd image plane
5: 2 inch space
6: 9" FL Fresnel(groves facing LCD)
7: 13 inch space
8: 13" FL lens Triplet (diylabs)
I tried moving everything closer to the lamp so the first fresnel would be about 6 inches but this just throws the side more out of focus. I dont have the glass yet to sandwitch the first fresnel. Could this be the remainder of the softness. |
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| ace3000_1 |
number 3 should be switched around with number 6, thats your problem, there is no way a frensel with a 13inch focal can collimate light corectly with a 9inch space, u got the frensels around the wrong way bud, try also if u can a 1inch gap inbetween the lcd and frensels.
Trev |
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| cruser |
dracul you have to sandwitch the top fresnel inbetween glass to focus the entire image because the fresnels are bowed
you dont have to do anything to the bottom one at all
and i have to agree with ace the fresnels seem to be backwards
just make sure the grooves face the lcd and bolth fresnels bow upwards twords the objective lens |
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| dracul |
One of the fresnel pieces is marked "top". Up until today I have been placing this lens first as in next to the lamp because it was the one making the larger light spot so I figured this was the 9 inch FL fresnel. I knew this was supposed to go next to the lamp so I was testing this method for days. The problem was I could not project the entire image. I would get a big round dot on the wall.
Today I tried switching the location of the fresnels (13 inch FL next to the lamp and 9 inch next to triplet) and bingo. Big improvement. I can now project the entire image, it was more even but still soft focus (and slightly dimmer) on the left and right edges).
Now you guys are saying the 9 inch FL fresnel(or the one throwing a larger light spot) should be next to the lamp. Well I have no idea what is going on because I would be regressing now.
Doesnt the fresnel half that is marked "top" mean it goes on top of your OHP which means it goes next to the triplet. Or this lens really a 13 FL while still throwing a wider beam?
Yeah I noticed the closer the fresnels are to the image plane the more even and easier it is to get the entire lcd projected and more even image but I did see fresnels rings slightly. |
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| dracul |
The fresnel I said is marked top is actually marked up. This is the lens I am using closest to the lens triplet.
I have sandwitched the fresnel before the lens triplet between 2 sheets of glass.
I am still getting soft focus on the sides. |
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| dracul |
| quote: | | It sounds like your focal lengths are off. What lamp are you using? and how is everything spaced out? are you using your own case or regular OHP? |
I am using a made box actually just a table. No mirror. I am using a 150 watt MH hqi lamp with a rectangular housing reflector that came with it. |
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| jcbklyny |
Since your having problems I say forget about what each fresnel says. Do a focal length test and you'll know for sure which lens is which. The shorter focal length should be mounted first, and the longer focal length should be on top or between the LCD and objective in your case. Grooves face towards one another and make sure your spacing is correct. It still just sounds like your focal lengths and mounts are out of whack.
And take crusers advice on the fresnels being bowed. I have never used DIYlabs or OHP fresnels so I dont have any experience with them. |
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| mhelin |
| quote: | Originally posted by dracul
I am using a made box actually just a table. No mirror. I am using a 150 watt MH hqi lamp with a rectangular housing reflector that came with it. |
Get spherical reflector. |
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| dracul |
| quote: | | id be fooling with the distance from the lamp to the frensel if i was u cos its definatley a focal problem in that area. |
Alright, so I am going to confirm the actual FL of each fresnel. How do I do this?
Lets say the shorter FL fresnel results in 8.9 inches. Then I place this same fresnel at exactly 8.9 inches from the center of the round part of the bulb right? How critical is the distance here?
What if the distance is 8.7 or 9.2? Would this throw the sides soft?
Next I space the lcd image plane 1 inch or 2 depending on rings than the longer FL fresnel 1 or 2 inches further again and than the objective lens triplet which can only go at one distance, the FL distance of the lens. In this case 12.97 inches from the lcd image plane. Correct?
| quote: | | Get spherical reflector. |
Is everyone is using a spherical reflector? There are people using no reflector and they are not having this problem.
To test if the reflector is the problem what if I throw the lamp into a mirror and have the mirror light enter the optics assembly path. |
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| dracul |
Ok. So I got the fresnels positioned the way you guys told me to:
Shorter Fl first then image plane than Longer Fl then objective. Both fresnels have groves facing the image plane or lcd.
I have not confirmed the actual Focal lengths yet. The problem remains.
I have however considered the lamp as a possible problem so I took some light readings with my footcandle meter.
Lamp to Light Meter Straight(no optics)at 9 inches= 1/4 light less on sides.
So without any fresnels the light is falling of on the sides by 1/2 stop at 9 inches from the bulb.
I then put the Short FL fresnel at 9 inches from lamp and take a reading on the other side or at 11 inches from lamp. The difference between centre and the sides is now 1 full stop. This means if 5000 Footcandles hits the centre 2500 hits the sides.
Since the lcd would come next obviously the same uneven ilumination would hit the lcd.
There are more optics to go but should we stop here and realize this is the problem?
If I remove the reflector and housing I am fairly certain that the uneven illumination will continue . It is an Osram hqi 150watt so I the size should not be an issue.
But a huge 400watt single ended would be more even at a short distance would it not? |
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| dracul |
| I tried throwing a diffussion type material in front of the lamp that I know would even the light out hitting the first fresnel but as it passes through all the other optics the results on the wall of the image is the same soft focus sides. So this makes me think its a fresnel or fresnels issue not a lamp issue. |
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| ace3000_1 |
dracul, it is definatley a frensel problem but what wont help is that light in its enclosure, the reflectors in them are ****, sorry if i sound rude but they are, u dont want to diffuse any light, the frensel collimates it over the entire lcd so forget about diffusing anything, if u difuse the light u will loose alot of light and u wont have any intensity to give u a decent throw or an intense image, what u need is a decent spherical reflector, the 9 inch frensel 9inches away from the bulbs arc or condenser, frensels have abit of give in them in their optics but experiment to get the best results, now cos u dont have a reflector place place the bulb and socket on somthing that wont burn, fixing it is better, now BE CAREFUL that bulb gets hot and will blow if anything falls on it, ok now place your 9 inch focal frensel above it 9 inches, then leave the 1 inch gap, now the lcd, then another 1 inch gap then the longer focal frensel and the triplet after, it should work, but if u have been given the frensels in some mix up of the same focal then it wont work, to me it sounds like its your focal and u need a decent condenser and reflector, your image is soft on the edges because perhaps u need a condenser to spread that light that bit more, but with well matched frensels with or without any condenser they will work, to get your frensels focal, place a table under a light in the house, now face the grouves to the light and lift the frensel slowly from the table until u see the light get to a small focal point, infact u should beable to see the bulb on the table, now measure that distance from frensel to the table, that is your focal for that frensel, do it to both and then u have the focal for both frensels and u will then see what goes where, anyway bud good luck and let us know on your findings.
Trev |
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| dracul |
Ace,| quote: | | to me it sounds like its your focal and u need a decent condenser and reflector, your image is soft on the edges because perhaps u need a condenser to spread that light that bit more |
So a condenser is small that sits in front of the bulb about and inch or less , spreads and sends the light more evenly towards the first fresnel? I think this will help.
I am sure I have 2 different FL fresnels. I will do FL test and confirm their FLs.
I removed the reflector and did a test with just the bulb. It was worse. The edges were softer it seemed. In any case it didnt improve. |
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| ace3000_1 |
| quote: | | I removed the reflector and did a test with just the bulb. It was worse. The edges were softer it seemed. In any case it didnt improve. |
yeah thats prety normal, the reflector that they use though are designed to partly difuse the light, try to get hold of a good shperical reflector, i can garentee u that it will be atleast 3x brighter then the one u have, well one with a enhanced alloy coating anyway, i did have a few and sold them off, i may be able to get more in the future im not sure at this stage.
Trev |
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| ace3000_1 |
| quote: | | So a condenser is small that sits in front of the bulb about and inch or less , spreads and sends the light more evenly towards the first fresnel? I think this will help. |
yep thats the one, not as far as an inch though about 1cm, ive got a few here that can be right on the bulb or about to a distance of 5cm, ive got about 8 different types, i tried one out the other week that i hadnt experimented with before and no joke its the brightest one ive seen also it spreads the light very wide with no hot spots and that was on a 150w cdm-t bulb, basically the same bulb u have but single ended and abit smaller in size, that was also in conjunction with a 50mm high precision shperical reflector.
Trev |
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| dracul |
Ok. I did the FL test on the Fresnels. The one I thought was 13 inch is actually a 9 inch. And the one I thought was 13 inch is actually 15inch but this didnt really matter.
So I got---
Lamp---7.75 inch space---9 inch FL fresnel--- 1.5inch space---Image plane---1.5 inch space----15 inch FL Fresnel---12.5 inch space----Objective
Distance from 9 inch FL Fresnel to Objective is 15 inches to back of triplet. Check!
When I put a paper on the the back of the objective I see the image of the bulb. Check!
Although the sides focus improved very slightly it is still soft.
So, sounds like I trouble shooted everything with the fresnels so the next thing to work on is the light source.
I mentioned the light uneveness hitting the image plane earlier. Does the light hitting the lcd not have to be even from side to side and top to bottom?
I thought condenser lenses focus the light to an even narrower beam not spread light? So the least I need now is a spherical reflector.
So if I get a condenser and put in infront of the bulb and then take light readings from side to side of the light hitting the first fresnel it will be more even right? Because right now its lousy. |
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| dracul |
Also I suspect a 400 watt single ended bulb will also be much more even since it is much larger. True or False?
I may upgrade to this very shortly because I feel I will need it but maybe not with condenser and spherical reflector. I want to project on a grey screen for richer blacks. |
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| dracul |
The only important part of the bulb is the centre right? My bulb is double ended so the reflector would have to be much larger than 50mm but I bring this up because if I had single ended bulb 50mm reflector would do it.
In conjuction with a spherical reflector, is bigger still better or if you use a condenser smaller is better. |
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| ace3000_1 |
| quote: | | Lamp---7.75 inch space---9 inch FL fresnel |
there should be 9inches there dracul |
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| ace3000_1 |
| quote: | | I mentioned the light uneveness hitting the image plane earlier. Does the light hitting the lcd not have to be even from side to side and top to bottom? |
ya its best to get it as even as posible cos then the frensel can do its job properly, but even without a condenser a frensel still can work with no problems, it depends on your fresnel, poor quality fresnels arent worth it, now that ive read a few issues with allan's newer fresnels im wondering about the quality of them, or is it just u guys not lining things up correctly, hm maybe poor QC at the factory.
Trev |
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| ace3000_1 |
| quote: | | I thought condenser lenses focus the light to an even narrower beam not spread light? So the least I need now is a spherical reflector. |
1 condenser lens will spread light, 2 of them facing front to front to each other will make the beam the size of the actual lens, it will make a channel of light and without a decent reflector the condenser cant perform its duties in the most eficient way.
Trev |
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| ace3000_1 |
| quote: | | The only important part of the bulb is the centre right? My bulb is double ended so the reflector would have to be much larger than 50mm but I bring this up because if I had single ended bulb 50mm reflector would do it. |
lol ya it is, its where the light comes from isnt it ? lol sorry bud just fooling with ya, the reflector being a size of 50mm is fine, unless your arc is over 40mm in length wich i doubt, i think your arc is 10mm from memory, mines 9mm, jcb's using a 50mm spherical reflector on his 400w and as far as i know its fine, the condenser realy should be the same size as the reflector too big of a condenser wont do too much, there are limits, i like to use the condenser the same size as the reflector with the reflector, bulb, and condenser evenly spaced, (at the correct distances ofcourse), that way all if not the majority of the light off of the reflector is going through the condenser, the light at the sides is at an angle that u cant realy use anyway so its wasted light and there isnt much we can do about that.
Trev |
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| dracul |
| Do they have 50mm reflectors for double ended bulbs? |
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| ace3000_1 |
heya dracul the reflector is round, 50mm and just sits under the burning arc under the bulb, i know what your thinking in where it sits behind the whole light but no it dont , just behind the burning arc it sits cos that is the point source of the light and that is what has to be reflected.
Trev |
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| dracul |
| quote: | | poor quality fresnels arent worth it, now that ive read a few issues with allan's newer fresnels im wondering about the quality of them, or is it just u guys not lining things up correctly, hm maybe poor QC at the factory. |
I just got marks on the fresnels from Alan. They look like 1/8 inch abrasions they are on the sides on both lenses pretty much on all sides especially the 15 inch one. I dont see them yet since the sides are soft at this point. He said they probably wont show up. |
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| dracul |
| quote: | | heya dracul the reflector is round, 50mm and just sits under the burning arc under the bulb, i know what your thinking in where it sits behind the whole light but no it dont , just behind the burning arc it sits cos that is the point source of the light and that is what has to be reflected. |
Ok. I am picturing it now. I will go and get one ASAP. I will search for more info on here. You have condensers for sale? |
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| ace3000_1 |
ya i got a few i sell them for $10 - $15 depending on what it is and what i paid for them, ill have a hunt around for some more reflectors, i havnt had much time in the last weeks to get more gear so i dont have much stock left, but condensers i have a few of.
here is a pic i drew up for a mate of mine who was wanting to design a simple ohp setup a while ago, i think this pic will help u picture what im talking about.
Trev |
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| dracul |
I found a spherical reflector. It is similar to a church cup thing someone posted on another thread. It is 100mm in diameter and fairly shiny.
The bad news is when I tested it the results were worse. The reason being was because now it projected a narrower beam towards the first fresnel. So what I had was about a 6 inch diameter hot spot hitting the back of the first fresnel and the rest much darker. Is this what you guys are getting with a small spherical reflector?
I tested the fresnels FL and they are positioned at the right distances. I have a Osram hqi 150 watt Powerstar MH bulb that should work without a reflector even. But all I get is soft focus sides due to what looks like drop in light intensity in those areas of the lcd plane.
Is it possible that the back Fresnel is just not large enough do a better job on focus eveness? But all of you are getting great results with the same gear I have. So what am I doing wrong?
My guess is that the problem lies with the light leaving the bulb not being spread enough or even enough but I cannot be sure.
I think the solution would be a much larger 400 watt single ended bulb. But I cannot be sure.
Before I invest in this how can I test that this is in fact the problem?
How can I confirm that the problem is with the fresnels? Is it possible the fresnels are lousy quality or one half is? Again is there a way of testing this and which fresnel? |
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| jcbklyny |
Well, the 150watt bulb is about a low as you can go as far as brightness goes... so a higher wattage bulb will help. But a spherical reflector doesnt really work without a condenser. The reflector just makes the arc brighter and allows the condenser to collect more light from the bulb.
And dont forget about the focal length of the reflector. It's a big reflector so I doubt it has a short focal length. The arc should be placed at the radius of the reflector... not the focal point. So if the focal point is 50mm the radius is 100mm. Thats huge for a 150 watt bulb. You would need a smaller reflector in that case. No larger then twice the arc size itself. |
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| dracul |
Is there any other way I can test if the light uneven ness coming out of the lamp is the problem? Or if there is a problem with the fresnels?
jcbklyny, You are using what size fresnels? Where did you get them from and are they both out of the image path? What is your spacing like? You have a 15 Inch lcd? |
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| jcbklyny |
I dont think there is a problem with the fresnels. The DIYLabs fresnels are not top of the line but I think they're doing the best they can with a 150watt source.
I still think the problem is your optical system and positioning.
- A smaller reflector with condenser lens will help. You need both to work the way you want it to. One or the other wont do it.
- A brighter light source will help.
- Double and triple checking your spacing will help.
All of the above should solve your problem.
I use custom cut fresnel lenses from AWI. The specs are:
312.4mm x 236.2mm with focal lengths of 225mm and 400mm.
I using the CMV 1512 LCD with both fresnels mounted behind (OHP style. Which is the reason for the 400mm focal length top fresnel.) I'm using a 400watt HPS retro-fit type outfit with spherical reflector and large condenser combo. I'll be updating my "Aluminum MK2" thread either tonight or tomorrow with pics and setup info so check there if you'd like to see more of my results. |
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| dracul |
There is really only one spacing I need to check. Bulb to 9 inch FL fresnel right? The spacing next is basically as close as possible without seeing rings. And the objective can only go at one distance which is to focus on the lcd image plane.
I discovered something strange. If I tilt the lamp housing down about 45 degrees I get a more even light. So I guessed the bulb axis was not dead centre with the centre of the first fresnel.
I then tried lowering the entire lamp housing (instead of tilting) but this did not work. It looks like the reflector is screwing things up but how does that make sense?
I am going to try to center the bare bulb without the reflector on the centre ring of the fresnel see if this helps.
My fresnels are 309mm square and the top fresnel is 381mm. Not to far off so i should still be able to do OHP style setup with the entire lcd image and nice and even right?
So the condenser lens will widen and even the beam out more?
I mentioned a larger bulb mainly because a 400 watt single ended is much much larger than my 150 watt and therefore much more even light going towards the first fresnel. |
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| dracul |
| Here are photos of my lamp and housing. Notice the tilt down that I had to do to get more even light. Lowering the housing while keeping it perpendicular to the first fresnel did not do the same thing. |
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| cruser |
dracul
i cant believe your getting a half way decient image at all with that light you are using scrap that damn shop light
i dont think150w is enough for a 15" lcd anyway i wouldnt use anything under 250w and definetly not a SHOPLIGHT
the field lens in that article you posted is what the split fresnel is
the top fresnel is considered a field lens it will more evenly light your lcd |
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| dracul |
Allright, so I lose the housing, reflector and get a 50mm spherical reflector and a condenser for top notch image right?
I tried putting the halfs together and out of the image path same OHP setup as jcbklyny and it worked no worse than splitting them and the lcd between the fresnels. So I think once I solve my lamp/source issue I will go this way I think. Woopie.
Btw, I just looked at brand new OHP projector at a store. They showed me a demo and guess what? I saw the same thing happening there. The sides were dimmer and softer although not quite as bad as my setup. He opened it up to for me. 50mm spherical with a 150watt single halogen. No condenser next to the bulb. The image was sharper in the centre though compared to what I got still. |
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| dracul |
| One other thing. I am still not sure how the bulb should be mounted in the socket and or how it should face the fresnel. Do you see the little bump on top and infront as well. Does this matter if its facing the image path. What is this for? |
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| dracul |
I got this email response from Edmund optics engineering department today:
Thank you for contacting Edmund Industrial Optics for your application
requirements. The problem should not be with your Fresnel lenses
because
they are more involved with collecting the light as opposed to focusing
the
image. The problem is most likely your projection lens which actually
focuses the image onto the screen or wall. [You may want to consult
with
the source of the objective lens and see if they can help you.] Please
let
me know if you have any additional questions. |
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| dracul |
| Btw, I tried using a candle as a light source and I was still getting darker sides although focus was nearly impossible to see since it was so dim. Same deal with the 200 watt house bulb. It was soft on the sides and dimmer. |
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| ace3000_1 |
| quote: | | Btw, I tried using a candle as a light source and I was still getting darker sides although focus was nearly impossible to see since it was so dim. Same deal with the 200 watt house bulb. It was soft on the sides and dimmer. |
did u try it with a sheet of paper on top of the frensel? just looking through it with your eyes all u will see is the light sorce, u need somthing on top and if u are going to use your eyes u need to stand way back so your out of the focal range, only then u can see the whole frensel lit with your eyes, atleast in what ive tested.
Trev |
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| dracul |
Ok. Will try that as well. But the image plane or Lcd is lit dim on the sides this is not hard to see. So the image plane is lit even more unevenly than the first fresnel. I asked edmundoptics if the light on the lcd should be even but they did not comment on that they said its most likely the objective that is causing the problem?
What do you think? I was thinking of lighting up a 3 foot x 3 foot textured wall with the lamp and focusing the objective to it. If the lens is functioning properly should I see an even sharp image edge to edge?
I find it hard to believe the problem is with the objective but stranger things have happened. |
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| ace3000_1 |
lol ya ok, stranger like your lcd cracking from pulling the polariser off? lol sorry just a joke, forget the projection lens and the top frensel for now, all u need to get is that lcd lit up fairly even on the first frensel, what your eyes will see the projection lens will see too so dont project anything yet, if u get the light over your lcd nice and even with the top frensel on it then u project it, and if the light isnt even when projected, then u can say its the projection lens thats at fault, but until then right now we cant tell and this lens is used in many other peoples projectors that do work fine so we will forget about that at the moment.
Trev |
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| dracul |
Made another discovery. I originally thought the soft areas on the screen are a result of dimly lit image plane area. Well now I know this is wrong.
I took a 2x 2 inch piece of tracing paper and held it behind the first fresnel in the center where the image was sharp. The image dimmed quite a bit but the focus remained same sharpness. I also tried the tracing paper between 9inch Fresnel and lcd with the same result. Then I held the tracing paper in other areas. The focus remained unchanged.
I also noticed that the image is also soft top and bottom but not as bad as the sides. The dimness is also present here.
So, only the center of the image is sharp. Why? Its not because the light is strongest there is it? My focals are not off I am pretty sure. Its not rocket science. So what else could it be?
Remember I said I tried the candle test and the light was still uneven on the screen? I will do this again cause it was dim so I could have been wrong. |
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| ace3000_1 |
Dracul how flat is that frensel?
Trev |
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| dracul |
| quote: | | all u need to get is that lcd lit up fairly even on the first frensel, what your eyes will see the projection lens will see too so dont project anything yet |
The only thing is I have spent over $800 us on this project so far and 3 months of waiting. I have still not enjoyed squat. So I would like to keep the budget somewhat under a retail projector.
If I have to buy another condenser and reflector with shipping to Argentina probably $60 usd and then also find out that the problem remains then buy another objective with shipping another $60 usd.
Did I mention the fresnels are scratched faily heavily. So that may show up also who knows. More waiting.... |
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| ace3000_1 |
| quote: | | The only thing is I have spent over $800 us on this project so far and 3 months of waiting. I have still not enjoyed squat. So I would like to keep the budget somewhat under a retail projector. |
Ya u have had a bad run of luck, thats why im trying to help u out, trying to get the most out of what u got now and trying not to spend any more money, i dont know who priced u $60 for shipping to argentina but thats abit high for a reflector and condenser, 3 months isnt such a bad wait, the way its going with mine it will be 3 months before its finnished lol, i dont have time latley to do any work on it, anyway the only thing u can do dracul is keep trying, it could very well be a simple mistake u are making in a test, and remeber all good things come to those who wait.
Trev |
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| dracul |
| quote: | | Dracul how flat is that frensel? |
I thought of that. I put the too pieces together exactly to match and sandwitched the double fresnel between 2 sheets of glass.
Ofcouse I did that to the top fresnel when they were split. When doing a split I only sandwitched the top fresnel. Just incase the frist fresnel also needed I grabbed the sides and arched it on the sides to see if it would make a difference in focus. NO. |
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| ace3000_1 |
| ok and u got the rings to the lcd? and have u tried it around the other way? |
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| dracul |
| quote: | | could very well be a simple mistake u are making in a test, and remeber all good things come to those who wait. |
That is my gut feeling also but I think I troubleshooted pretty much everything. I mean its really not that complicated and there are not that many variables to this project. But you are right, all I can do is keep troubleshooting. |
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| dracul |
| quote: | | ok and u got the rings to the lcd? and have u tried it around the other way? |
When split yes. The rings or grooves face the lcd. I tried them facing out , grooves to lamp, grooves to objective. |
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| dracul |
| grooves to lcd was the best and the only obvious choice. |
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| ace3000_1 |
| quote: | | That is my gut feeling also but I think I troubleshooted pretty much everything. I mean its really not that complicated and there are not that many variables to this project. But you are right, all I can do is keep troubleshooting. |
Yep thats all u can do, u thought in making a soup ladele reflector for a make do test? u can use the magnifying glass as a condenser lens it may not put out such a wide image though, i think this could be your next test.
Trev |
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| ace3000_1 |
i think with your image not focused on the edges it sounds to me u need a condenser, and your talking about not projecting it i hope, i hope your saying that it looks out of focus on the edges to your eyes, also talk to allan at diy labs, he may give u a condenser for free if your nice enough lol and he will know its for testing.
Trev |
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| dracul |
| quote: | | u thought in making a soup ladele reflector for a make do test? u can use the magnifying glass as a condenser lens it may not put out such a wide image though, i think this could be your next test |
I tried the reflector test already. I used a high polish icecream cup. The kind someone posted on here that looks like a church cup. 100mm diameter and about 1 inch deep. Ofcouse I could not place the arc at the radius just right up against the outside or top of cup. The result was a 6 inch diameter hot spot hitting the back of the first fresnel. |
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| dracul |
The reflector test was without the magnifying glass though.
I quickly tried a magnifying glass. I didnt notice a spread difference but will try again just incase. |
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| ace3000_1 |
| quote: | | I tried the reflector test already. I used a high polish icecream cup. The kind someone posted on here that looks like a church cup. 100mm diameter and about 1 inch deep. Ofcouse I could not place the arc at the radius just right up against the outside or top of cup. The result was a 6 inch diameter hot spot hitting the back of the first fresnel. |
k then cut the sides out of it so the bulb can go in it further and the light beam can be reflected wider, try that |
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| dracul |
| quote: | | i think with your image not focused on the edges it sounds to me u need a condenser, and your talking about not projecting it i hope, i hope your saying that it looks out of focus on the edges to your eyes, |
Right it looks out of focus on the edges to my eyes on the wall.
Are you saying you dont agree that the test with the trace paper proves its not a light dimness issue resulting in soft focus? |
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| ace3000_1 |
| quote: | | Are you saying you dont agree that the test with the trace paper proves its not a light dimness issue relating to soft focus? |
i dont know where that came from lol but with the triplet the image should be perfectly focused from side to side, what i meant was before i wouldnt worry about testing it projecting yet and im curious if your still projecting it to get your results, u are using a triplet right? hey and if u are, what way have u got that around? have u tried to turn it around to see if it makes a difference?
Trev |
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| ace3000_1 |
| define soft focus, is it in focus to the center or out of focus to the center? |
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| dracul |
| quote: | | i dont know where that came from lol but with the triplet the image should be perfectly focused from side to side, what i mean was before i wouldnt worry about testing it projecting yet and im curious if your still projecting it to get your results, u are using a triplet right? |
I guess you missed that post. Ill find it for you. Yes I am testing by projecting. How else can I test? If you mean just get even light on the lcd well yes that I could do without projecting but I already determined that focus is the biggest problem not dimness. And dimness is got nothing to do with soft focus anymore according to the trace paper test I did. You tell me. |
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| ace3000_1 |
| ok i must have missed a few things, so what your telling mne now is that the lcd or what ever your using is lit up from sides to center evenly? but when projected its dim on the edges and the center is brighter? |
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| dracul |
| quote: | | define soft focus, is it in focus to the center or out of focus to the center? |
It is only sharp sharp in the center. The left and right sides are out of focus. The top and bottom is also out of focus but not as much.You can read 8 point text but no way you would see lcd pixels I would think.
Do you think its possible the short throw is causing this problem?
But then everyone is got a short throw. |
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| ace3000_1 |
| how short is your throw? i supose 4ft lol i dont think so if others are using it, but if u got it like 1ft from the wall it might |
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| dracul |
| quote: | | ok i must have missed a few things, so what your telling mne now is that the lcd or what ever your using is lit up from sides to center evenly? |
No, I am saying the out of focus is not a result of uneven lighting.
That is what the trace paper test proved.
| quote: | | but when projected its dim on the edges and the center is brighter? |
Right. |
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| dracul |
| quote: | | how short is your throw? |
I went a little closer to the wall starting today. I didnt measure but I would guess 6 feet or 6.5 for 7.5 image width. |
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| ace3000_1 |
| quote: | | but when projected its dim on the edges and the center is brighter? |
ok well thats your light source with no reflector and condenser, now try this, dont look at whats on the wall projected, look at the top frensel with the trace paper in there and tell me what u see, at the focal where the lens is or just before it, tell me how even the light is and tell me how focused it looks, if it looks fine then u got a problem with the triplet.Put your head so your eyes focus on the image. |
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| dracul |
| quote: | | ok well thats your light source with no reflector and condenser, now try this, dont look at whats on the wall projected, look at the top frensel with the trace paper in there and tell me what u see, at the focal where the lens is or just before it, tell me how even the light is and tell me how focused it looks, if it looks fine then u got a problem with the triplet. |
Im not clear on this. You want me to place trace paper over the top fresnel covering it entirely? Then you want me to look at the image on the top fresnel/trace combination from about where the triplet would be? |
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| ace3000_1 |
| ok u have light source, then first frensel at 9inches, then the trace paper u have, then the top frensel, then your head lol and tell me how well lit up the sides of the trace paper looks and what the focus looks like looking through the top frensel at a distance where the projection lens is and also move your head back or forward to try and focus the image to your eyes and tell me what that looks like |
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| dracul |
| Ok. I get it. Will go home and try this now and let you know tomorrow. Thanks. |
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| ace3000_1 |
if that all looks good then its definatley the triplet, try then to move the top frensel to suit the triplet, the triplet shouldnt be doing this but maybe its got somthing to do with the distance between the top and bottom frensels, if no go on that then i think try and get a hold of allan to see what u can do about a replacement triplet, cos it may well have a manufacturing fault.
have a nice night
Trev |
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| dracul |
The good news is I put my head about 2 feet past the objective looking at the fresnels image combo and I saw magic. I was using the 200 watt house bulb with the arc visible. It looked great. Very even and at the centre I saw the ever so bright upside down bulb and the blinding arc of the bulb. It was very sharp.
So the bad news is I have a non functioning triplet that just cost me 1 week of my time and much more now that I need to get another one.
| quote: | | try then to move the top frensel to suit the triplet, the triplet |
Ok, Ill try this again but I m pretty sure I messed with this over and over. The objective can only go at one distance. The back or first fresnel can only go at 9 inches and the top one I noticed can not go further than about 3 inches from lcd. Either way the sides are soft and darker.
So the light uneven ness is also caused by the objective now. We can be sure of this? Yes? |
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| ace3000_1 |
| quote: | | Ok, Ill try this again but I m pretty sure I messed with this over and over. The objective can only go at one distance. The back or first fresnel can only go at 9 inches and the top one I noticed can not go further than about 3 inches from lcd. Either way the sides are soft and darker. |
ok now if u didnt use the triplet at all in this test and just your eyes then yess it seems the triplet isnt getting all of the image at the right angle, so what u need to do is ajust only the top fresel to get all of the image into the triplet, remeber the top frensel turns the light into a cone? well i think in your case that cone is over shooting the triplet, this is meaning that the cone at where the triplet is , is too big, so we need to make that smaller to fit all into the triplet, and the only way to do this is to ajust the top frensel, try with the top frensel against the image plane then back it away slowly, the top frensel shouldnt realy be any more then 1inch from the image plane, as for different lenses and some of the wired stuff ive had, in my last projector i just sold, i couldnt use the copy lens im using on this new one im building, it would work fine with a singlet but not a doublet nor a triplet, it was my frensel, the frensel was not collimating enough light for a high quality lens, the more of a higher quality lens u use for projection the pickier they get, (abit like a woman realy lol) so inorder for a better projection lens to work u will need a higher quality frensel and other components, in my new projector it works fine, and i could of had it working in my old projector, all i needed was another frensel, now in your case u have a good frensel and triplet so it should work, if the triplet has a manufacturing fault then no way will it work corect, if it cant be fully focused from the center to the edges then it has a fault, the light loss on the edges in this case is normal as ive stated in another thread about how that lens is too small for our 15inch setups and looses light on the edges, the only way to compensate the loss on the edges is to use a reflector and condenser, realy to be honest a condenser , reflector, and a 100mm clear diameter triplet is the way to go, i can asure u that if we wer all using this combination we wouldnt be having any problem with light and that the 250w mh would be more then enough and probally would output 800lm ansi +, so what id do now dracul is try to shorten the focal in the area u have between the triplet and the first frensel, the first frensel stays where it is, the lcd next and the top frensel has to come closer to the image plane to make the cone smaller for where the triplet has to stay to be in focus.
Trev |
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| dracul |
| quote: | | the top frensel shouldnt realy be any more then 1inch from the image plane |
Tried that.
| quote: | | ok now if u didnt use the triplet at all in this test and just your eyes then yess it seems the triplet isnt getting all of the image at the right angle, so what u need to do is ajust only the top fresel to get all of the image into the triplet, remeber the top frensel turns the light into a cone? well i think in your case that cone is over shooting the triplet, this is meaning that the cone at where the triplet is , is too big, so we need to make that smaller to fit all into the triplet, and the only way to do this is to ajust the top frensel |
I played and played with the top fresnel. As you said it cant be too far from the image plane. Btw the hot cone of light fits just fine in the back of the objective. There is ofcourse spill light that is much weaker but my understanding is you just need to get the arc area entering the triplet. This is no problem. I can see the image of the arc on the back of the lens (with paper there).
| quote: | | the top frensel has to come closer to the image plane to make the cone smaller for where the triplet has to stay to be in focus. |
Yes I noticed this. When placing the the top fresnel right up against the image plane I get the best results. But its still soft focus and ofcourse I see the fresnel rings.
I dont think this cow has anymore milk. Remember I put in about 40 hours of messing around. |
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| dracul |
| But if you can think of any other test that can confirm the objective is faulty or not let me know. |
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| dracul |
Ace, does this ring a bell?
| quote: |
Ace_3000
According to another post I read somewhere in this forum our DIY projectors which generally have a relatively short throw distance from the projector to the screen have a relativly large projection angle. This means that the light coming from the lens hits the furthest edges of the screen at a larger then desirable angle, and so the outer edges of the screen will be darker than the middle because lass of the light is reflected back to the viewer. A curved screen can help minimize this effect.
Hezz
ya your right hezz on that note, and if the projection lens is small like the diylabs one the edges are also not as bright, another thing is if the lens is too close or close to the lcd it doesnt nesersearly cut the lcd off but it will be very dim on the edges because of the veiwing angle of the lcd's properties are out compared to the center veiwing angle where the lens is, not only that but the property of the lens isnt designed to handle those sorts of wider angles to project a perfect image, a good rule formula to follow is always try to find a lens that is no smaller than 1/10th scale of the lcd, that way it will be bright, the image will be projected more so without any deformalities and the projected image will have alot more of a uniform brightness over the entire area, when i got the diylabs triplet i was disapointed, it was smaller then what it says on his site, its not a 80mm triplet, its a 65mm triplet.
Trev |
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| ace3000_1 |
ya thats what im going on about the diylabs lens isnt 80mm its realy a 65mm it should be 80mm clear lens diameter to work right at the minimum but the 65 does work , its just the light u will have to trade of, all triplet lenses are designed to have different optimised angles and this lens is a wide angle lens, but i mean come on allan and the ohp crew not this wide, its pathetic its over the mark getting into the negative afects of the lens, the best part of any lens dracul is the center, it dont matter what lens it is or how much u pay, the wider u go in the angle the worse the image will get on the sides, and in this case we all loose light with this triplet on the outer part of the image cos its out of range of the lens capibilites, right on the border zone of it doing its job and performing and where it cant perform, this is a ohp triplet lens dracul, its cheap and nasty and designed to be on the limit to save the manufactuer costs, ohp's are cheap and nasty, the best lens i think dracul for quality versus price is a copy lens , a triplet of course, they are a very highly engineed lens and often found alot cheaper then a ohp triplet when sold at surplus stores, ill have a hunt around for u dracul and see what i can find. Another thing i might add is that a stage on a ohp is smaller then a 15inch lcd.
Trev |
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| ace3000_1 |
ill put this in the right way dracul, its not realy allans fault nor the ohp's manufacturers fault, its realy ours cos we are trying to get somthing out of somthing thats on the limits in the first place, and taking it further will only cost us light and picture quality.
Trev |
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| dracul |
Sounds like you are saying even with a functioning diylabs triplet the picture would not be great.
Had I know that, I would have never bought it. I kind of regret not buying a commercial projector now. |
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| ace3000_1 |
| lol no no dracul its not that bad, the lens works fine in most setup's but what im saying is we are pushing that lens into the limit of its capibilites and dont be suprised when u get dark edges on your image, just that |
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| diylabs |
Sorry that I couldn't have helped sooner - I haven't been following the forums as much as I used to.
Lighting:
How bright your light source won't make any difference in how focused your image is. So even if the center of your image is 100 times as bright as the outer edge, they should both be focused exactly the same. Also, your light source needs to be a point source, which is why shop lights make a terrible light source for projectors. Those reflectors are made to act as a flood light, but we need it to be the exact opposite. Long ago I tried many different shop lights because they were very inexpensive and very bright, but it took me a while to figure out that the reflector was the reason none of them worked. Oh well - now I have a few extra shop lights in my basement!
Lenses:
The fresnel lenses I carry are also from AWI, so you and I are probably using the same fresnel lens, or at least of the same manufacturing quality. The triplet lenses are originally meant for the high end 3M overhead projectors, but 3M would give me $100 as the lowest price possible for buying a lens, so I decided to buy them in bulk from another vender and undersell them ... same lens, but I don't charge such a ridiculous markup on them. Just think - if I can offer them for about $30, then 3M must be making a killing off of them because they can certainly afford to buy in larger quantities than I can!
The triplet lens that I sell is as good as can be expected for what we are doing with them. As Trever said, most lenses simply aren't meant for image sources larger tham about 80mm, so our 12 and 15" LCD panels are certainly large image sources! If you are getting anything less than a perfectly sharp image from one of my triplets, then either the lens is damaged or the setup might not be quite right. Perhaps if you could either post or email me a picture of your entire setup, then I could help you solve your problem, but I suspect that it is your reflector that is causing the blurry image - light coming from the reflector hits both the fresnel and the projection lens at the wrong angle, causing blurriness. Since the light hitting the center of your panel must come in at a straight angle, that would explain why the center of your image is the only part that is in focus.
Good luck with everything. If we do determine that the triplet lens is at fault, then I will certainly send you a new one, although I've never had that happen before out of nearly 1000 lenses, so I'm confident that something else is at play (the reflector) |
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| dracul |
Ok. That clarifies some things Alan. Thanks. Sounds like if the point source is to wide such as a 3 inch house bulb the angles are too extreme entering the first fresnel so NFG.
Sound to me then that the best source is the smallest source. The only problem is a smaller source is also less even right?
So I guess there is sweet spot for size.
So now it makes sense that using a large reflector such as in my pix this cause beams to come from too extreme angles. I get it.
1.Now if this infact was the problem then I should next use the bare bulb which I tried briefly because of the eyestrain. But I am going to do try this again now that I have new knowledge.
Lets assume that I sandwitch the fresnels as one as they were before split for the test to minimize variables. The grooves should face each other and fit perfetly on the corners so the cicular groves match up. Check.
2.Centre the point source arc to the centre of the fresnel and place it as it the Fresnels FL. When the fresnels have 0 distance between them the Back FL is different. According to the FL test its around 5 or 6 inches. Cant remember offhand.
3. Next place the image plane device about 1.5 inches away
4. Focus the objective to the image plane. There is only one option for distance here and that is 13 inches or the FL of the objective. Everything falls in to place after I do this. The arc is seen in the back of the objective and fits fine within the diameter.
Is this right?
Will try this again. This time with some WELDING GOGGLES LOL! |
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| ace3000_1 |
heya dracul, the light u have, the mh is fine , all u need is that condenser and reflector like i told u, to make it a proper point source.
nice post allan btw, makes things abit easier to understand, u got a better way with words then what i have lol.
Trev |
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| brainchild |
| dracul, sounds like you got it buddy...that's my exact setup and I don't have any issues at all...I'm not using a reflector or a small glass condensor (the fresnel after the lamp is a condensor)....so there's no reason you shouldn't get good results unless you have defective stuff. I'm using pretty much the same lens Alan sells and it's fine...also if you've split your fresnels and now want to put them back together, you'd better pay careful attention to the alignment, if they are just slightly out of alignment with each other you'll see a starburst pattern. |
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| dracul |
Brainchild, are you using a single ended 400watt MH? I cant remember.
I want to buy the welding gogles before I test the bare bulb again but I tilted the lamp housing verticaly as a test. The sides were still soft but sharper than the housing horizontal where the angles hitting the the fresnel are steeper. |
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| brainchild |
yeah man...MH400U...the beast
$15 |
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| diylabs |
Dracul, what you wrote sounds nearly correct, but I do have some comments. Your front fresnel focal length should be between 12" and 15". That focal length doesn't change even if you pull the fresnel halves apart, although it might appear that way once they are split if the rear fresnel isn't at the correct distance from the light source.
Also, your light dispersion actually gets more even as you decrease the size of your light source; although I know what you are thinking. Ideally, we would actually prefer a light source that is infinitely small. That is why large format projectors (like at movie theatres) use a XENON light source with an arc that is only a few mm in length! That type of technology is way to expensive for us (about $1500 per unit), but metal halides with 40mm arcs are nearly as good.
I agree with Trev that your metal halide would be fine if you use a smaller reflector with a condenser lens. You reflector shouldn't be any larger in diameter than the back side of your objective lense (smaller is better here too), but what's more important is that the reflector be a uniform shape. There are lots of ideas about whether to use parabolic, ellipsoidal, or spherical reflectors, but the truth is that they all work to some extent as long as the are of a uniform shape (not like a shop lamp reflector). Thus, you should be able to get your projector working immediately by removing everything from your light source except for the lamp itself. Then you can make it brighter by toying with different reflectors and a condenser lens, but the important thing is for you to get a sharp image first - you'll enjoy working on your projector much more once you realize that it will work!
| quote: | Originally posted by ace3000_1
nice post allan btw, makes things abit easier to understand, u got a better way with words then what i have lol.
|
Trev, I appreciate the kudos ... actually I had the benefit of being able to see everything guys have been talking about for the past couple of weeks all in one sitting, so everything was fresh in my mind when I wrote the reply. I agree with most of what you said, and you were doing a fine job. The forums can be great! I get emails like this every day for the past year, so I've gotten REALLY good at troubleshooting!
Hey, do either of you guys have a condenser lens yet? How about a little Christmas gift from DIY Labs - I'll even pay shipping as long as it's within the US. Email me about it if you'd like one. Cheers! |
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| dracul |
| quote: | | Your front fresnel focal length should be between 12" and 15". That focal length doesn't change even if you pull the fresnel halves apart, |
I regulate this by the objective.
I put my first or bottom fresnel at 5 or 6 inches than imager than top fresnel with these separated 1.5 to 2 inches. Then I focus my objective to the image plane. Since objective to imager is 13 inches then objective to top fresnel would be 1.5 to 2 inches less.
So 11 to 11.5 inches. If I go 12 inches I either have to put the top fresnel closer to the image plane or focus a 13 inch FL fresnel at 14 inches? Can you explain please? |
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| dracul |
| quote: | | Also, your light dispersion actually gets more even as you decrease the size of your light source; although I know what you are thinking. Ideally, we would actually prefer a light source that is infinitely small. |
So since edges may be an issue with such wide angle triplets we are using, could I possible get a more even ilumination image on the screen if I use a smaller arc such as 150 hqi double ended versus a 400 watt single ended monster? |
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| jcbklyny |
| Alan, if your fresnels are from AWI why are you buying the doublets for Overheads? After talking with them they arent the same as the singles they carry. |
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| diylabs |
| quote: | Originally posted by dracul
...could I possible get a more even ilumination image on the screen if I use a smaller arc such as 150 hqi double ended versus a 400 watt single ended monster? |
In a word - yes. Mogul lamps are rather bulky and their arc (for the 400w) is about 80mm, which is just too large for the backside of most objective lenses, including my triplet lens. That is one of the benefits of my 250w double-ended HQI as opposed to a Mogul 250w metal halide - smaller arc length. Another benefit to the HQI's is that they are small enough that you can get a condenser lens to fit much closer to the arc, collecting potentially MUCH more light. My current project is to find a 400w lamp that is roughly the same size as the 250w that I carry now, but I suspect that finding an appropriate ballast may be tricky.
| quote: | Originally posted by jcbklyny
Alan, if your fresnels are from AWI why are you buying the doublets for Overheads? After talking with them they arent the same as the singles they carry. |
I don't use doublet lenses for anything. The triplet lenses that I buy are made for high end overhead projectors that are used with video equipment like we are using. That makes them an ideal solution considering the cost involved. I don't know what you meant by "aren't they the same as the singles" ... doublets aren't as good as triplets and single meniscus lenses are downright lousy for projection. If you've already got a doublet and don't have much money to invest, then wait until later to upgrade to a triplet - a doublet is "good enough" for now - but if you're using a singlet, then definitely upgrade to a triplet - you won't believe the difference it will make!
Hopefully I understood correctly what you were talking about with the question you posted. Let me know if I missed something and I'll try to answer you better. |
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| jcbklyny |
| I was talking about the fresnel lenses... you buy their overhead fresnels... when their singles are much better suited for our project. Granted they cost alot more... but they're worth it. |
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| dracul |
Ok. I got my projector all optics mounted now and looks like my triplet is fine but I thing the dimmer sides is what is causing an illusion of soft focus because I am using black text on a trasparency.
So should I be getting even ulumination from side to side for a 9 x 12 image with 12.2 x12.2 fresnels from diylabs?
Why is it mentioned somewhere that the fresnel has to be larger than the lcd and yet many of you have been able to do this successfully with a 15 inch lcd (9x12 image) and diylabs fresnels? |
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