Jcbklny,
The problem is not that you have been saying that people are cheap, the problem is that you seem to have an attitude in the way you post. You could be the nicest guy in the world, but the way I read your posts, it seems like you have a chip on your sholder. Some of your posts are very informative, and I guess you can say whatever you want. I have just been itching to post something like this for awhile, so I did. Like I said, I would be the first to tell you what a great job you have done. I have been here for a long time, I might not be a "heavy poster", but I have been reading on this forum for quite some time. I hope to see those pictures soon, just incase you have discovered the next best thing. No hard feeling, I just wanted to get it off my chest.
Steve
P.S.
If you "could care less"......why dont you?
The problem is not that you have been saying that people are cheap, the problem is that you seem to have an attitude in the way you post. You could be the nicest guy in the world, but the way I read your posts, it seems like you have a chip on your sholder. Some of your posts are very informative, and I guess you can say whatever you want. I have just been itching to post something like this for awhile, so I did. Like I said, I would be the first to tell you what a great job you have done. I have been here for a long time, I might not be a "heavy poster", but I have been reading on this forum for quite some time. I hope to see those pictures soon, just incase you have discovered the next best thing. No hard feeling, I just wanted to get it off my chest.
Steve
P.S.
If you "could care less"......why dont you?
brainchild
ive got a lp220 pro projector here that uses 2 frensels i dont see a problem with text or ghosting, its clear as, how old was the article u posted?
Trev
ive got a lp220 pro projector here that uses 2 frensels i dont see a problem with text or ghosting, its clear as, how old was the article u posted?
Trev
ROTFLMAO
With correct design, modern manufacturing methods, and new
proprietary processes, Fresnel lenses are being successfully
incorporated in new high definition rear projection systems.
HAHAHAHAHAHAHA
With correct design, modern manufacturing methods, and new
proprietary processes, Fresnel lenses are being successfully
incorporated in new high definition rear projection systems.
HAHAHAHAHAHAHA
brainchild
lol yeah well its late here lol, i see u said u got bad resalts when putting a frensel up front, was your focals fully or closly within their focals?
trev
lol yeah well its late here lol, i see u said u got bad resalts when putting a frensel up front, was your focals fully or closly within their focals?
trev
look the guy who gave the conclusion quote is winning now everyone.😱 the photo is superfluous though, you should include a transparent ruler or a sweety wrapper next to it so that we can see how sharp it actually is relative to the camera quality.
i have just examined a old lcd from a laptop on the Geha OHP and the image is stunningly good. i really dont understand what a different fresnel than the ohp one is likely to acheive apart from erasing the concentric rings.
in my opinion these fresnel tricks are just be a way to make an equivalent of the fresnel already in the OHP just without the circle marks right? i mean guys please state the exact goals of your manipulations and the results with some paintpad squiggles that's all, any noob trying to glean info on here will be quite confused at the vague discussion here. all in all the lcd just has refractive properties of a dull peice of plastic like a cider bottle when you are just trying to focus it through one point?
i think maybe we would all agree more if we did more scientific experiments.
i really dont understand talk of 60 degrees this and that becuase the panel sits perpandicular to the source and projection right? my 60 cents
about the vibes, did anyone see that tribe called quest song lately... all the love in the world,
lalala. jerry! jerry! yo the best!
omg the others are coming, noo! 
Jerry sais
the most steadfast members of technical forums just say what they think, why they think it, along with photos and documents. reproaching grumpy posts or misconstruing over enthusiasm as arrogance is something that you have to do really unconfontationally and by example or humour.
i have just examined a old lcd from a laptop on the Geha OHP and the image is stunningly good. i really dont understand what a different fresnel than the ohp one is likely to acheive apart from erasing the concentric rings.
in my opinion these fresnel tricks are just be a way to make an equivalent of the fresnel already in the OHP just without the circle marks right? i mean guys please state the exact goals of your manipulations and the results with some paintpad squiggles that's all, any noob trying to glean info on here will be quite confused at the vague discussion here. all in all the lcd just has refractive properties of a dull peice of plastic like a cider bottle when you are just trying to focus it through one point?
i think maybe we would all agree more if we did more scientific experiments.
i really dont understand talk of 60 degrees this and that becuase the panel sits perpandicular to the source and projection right? my 60 cents
about the vibes, did anyone see that tribe called quest song lately... all the love in the world,
lalala. jerry! jerry! yo the best! omg the others are coming, noo! Jerry sais
the most steadfast members of technical forums just say what they think, why they think it, along with photos and documents. reproaching grumpy posts or misconstruing over enthusiasm as arrogance is something that you have to do really unconfontationally and by example or humour. 
i know the pic is blurry but thats because i dont have a tripod to put the camera on and i have a shaky hand
i just posted the pic to show text is not ghosting with the front fresnel in place its an old pic and i dont have a pj to take pictures
of right now
so when you get your camera and finaly finish your tutorial and post some pics i will be very excited to see them
im not posting to start arguments im just stating facts that i have
concluded in the prosess of building pj's im not a photographer so
dont expect the pictures to be amazing but in real life believe me they are
i dont even own a pj i cant build them fast enough to build my own
and i have to say this one more time if you see rings and your image is distorted in any way with the fresnel in front of the lcd
its too close to the lcd 2" is the sweet spot
at 2 " with no image on the lcd i can see a perfect screen door
and all the sub pixels in perfect focus to say anything else would be a lie
im not saying that the front fresnel dosent impinge on the quality
of the image im sure the image would be sharper without it there
but to say the image will be blurry and have rings is just lieing to ppl
i would never steer anyone in the wrong direction i came
to this fourm from getting burned on the 100"tv thing on ebay
and the info i learned here is pricless i try to post everything
i do to help others its the least i can do
you have to understand ppl come here to save money on a
pj and $220 is quite a substancial savings for a fresnel alone
it dosent mean they are cheap just practial "why spend it if
you dont have to"
im working on another pj now so i will get a tripod and do extensive pictures on this subjuct so we can compare the diference when you get your camera not that pictures will
be much help it will be fun
and by the way i have ordered 2 fresnels from mr stephen woo
at awi for my pj so im not knocking you paying $250 for the fresnels but for a 15" it seems a waste they are no better than the diylabs fresnel just bigger well i guess bigger is better
oh i almost forgott where are the "rules" that have ben set for
projection optics i would love to look at them if they use fresnels in front of the lcd in comercial pj's i want to send them the link to the "rules" as well so they can straighten their act out 😀
i just posted the pic to show text is not ghosting with the front fresnel in place its an old pic and i dont have a pj to take pictures
of right now
so when you get your camera and finaly finish your tutorial and post some pics i will be very excited to see them
im not posting to start arguments im just stating facts that i have
concluded in the prosess of building pj's im not a photographer so
dont expect the pictures to be amazing but in real life believe me they are
i dont even own a pj i cant build them fast enough to build my own
and i have to say this one more time if you see rings and your image is distorted in any way with the fresnel in front of the lcd
its too close to the lcd 2" is the sweet spot
at 2 " with no image on the lcd i can see a perfect screen door
and all the sub pixels in perfect focus to say anything else would be a lie
im not saying that the front fresnel dosent impinge on the quality
of the image im sure the image would be sharper without it there
but to say the image will be blurry and have rings is just lieing to ppl
i would never steer anyone in the wrong direction i came
to this fourm from getting burned on the 100"tv thing on ebay
and the info i learned here is pricless i try to post everything
i do to help others its the least i can do
you have to understand ppl come here to save money on a
pj and $220 is quite a substancial savings for a fresnel alone
it dosent mean they are cheap just practial "why spend it if
you dont have to"
im working on another pj now so i will get a tripod and do extensive pictures on this subjuct so we can compare the diference when you get your camera not that pictures will
be much help it will be fun
and by the way i have ordered 2 fresnels from mr stephen woo
at awi for my pj so im not knocking you paying $250 for the fresnels but for a 15" it seems a waste they are no better than the diylabs fresnel just bigger well i guess bigger is better
oh i almost forgott where are the "rules" that have ben set for
projection optics i would love to look at them if they use fresnels in front of the lcd in comercial pj's i want to send them the link to the "rules" as well so they can straighten their act out 😀
the sweet spot for having no fresnel lines is just at the end of the height at which the fresnel details come into focus. it makes me wonder why on earth ohp people place the fresnel right under the projection glass rather than a inch under to have a perfect image, isnt this strange?
you could try taking photos with the camera sat on the same table as the ohp, isnt it easy?
you could try taking photos with the camera sat on the same table as the ohp, isnt it easy?
vvvvvvvv
ill tell u an easier way, why not just get the frensel place it behind the lcd with the lcd off put a desk lamp in the ohp or similar setup for a rough light source so u dont get bad eyestrain nor damage to your eyes, and just move the frensel back from the lcd till u cant see the rings, infact until u can just see the rings cos that will be out of focus for the projection lens when its focused to the lcd not the bottom frensel, cruser is correct about 2inches is a good clearence, however on the smaller and different setups i make 1 inch is suficient thus i am using different frensels and componets, but 2inches is fine, any more than that then u are running out of frensel area to lcd area coverage, may i ask what setup u have currently vvvv or plans for a setup?
Trev
ill tell u an easier way, why not just get the frensel place it behind the lcd with the lcd off put a desk lamp in the ohp or similar setup for a rough light source so u dont get bad eyestrain nor damage to your eyes, and just move the frensel back from the lcd till u cant see the rings, infact until u can just see the rings cos that will be out of focus for the projection lens when its focused to the lcd not the bottom frensel, cruser is correct about 2inches is a good clearence, however on the smaller and different setups i make 1 inch is suficient thus i am using different frensels and componets, but 2inches is fine, any more than that then u are running out of frensel area to lcd area coverage, may i ask what setup u have currently vvvv or plans for a setup?
Trev
vvvvvvv
a couple of reasons why ohp manufacturers put the frensel right under the stage glass, 1 cos quaility doesnt realy matter cos u are just projecting a transparent sheet, 2 the brightness of the bulb is not bright enough to emit such informalities to baddly, 3 its brighter closer to the frensel then farther, 4 limited room, 5 generally ohps are considered a cheap projection alternative for a class room or lecture theater, the next step up is either a projection panel wich i think isnt worth it unless u have a decent high power projector basically cos of light issues and even then that is considerd a cheap alternative or going for a pro portible projector being lcd back in those days, a ohp is a cheap design, it works well, and personally i think is a great little machine, but u get what u pay for, that is why people in here modd these ohps and build their own to perfect them where the manufactuer didnt and didnt need to for its intended operational use, by the way i noticed that u said somthing about guys or us in here not using good quality frensels and u cant understand why we are fooling with a peice of dull plastic, well we are using high grade optical so called peices of plastic called frensel lenses, and they arent dull, infact if u have one they are crystal clear and not only do they redirect light but they are also a lens designed not to difuse light but redirect it.
Trev
a couple of reasons why ohp manufacturers put the frensel right under the stage glass, 1 cos quaility doesnt realy matter cos u are just projecting a transparent sheet, 2 the brightness of the bulb is not bright enough to emit such informalities to baddly, 3 its brighter closer to the frensel then farther, 4 limited room, 5 generally ohps are considered a cheap projection alternative for a class room or lecture theater, the next step up is either a projection panel wich i think isnt worth it unless u have a decent high power projector basically cos of light issues and even then that is considerd a cheap alternative or going for a pro portible projector being lcd back in those days, a ohp is a cheap design, it works well, and personally i think is a great little machine, but u get what u pay for, that is why people in here modd these ohps and build their own to perfect them where the manufactuer didnt and didnt need to for its intended operational use, by the way i noticed that u said somthing about guys or us in here not using good quality frensels and u cant understand why we are fooling with a peice of dull plastic, well we are using high grade optical so called peices of plastic called frensel lenses, and they arent dull, infact if u have one they are crystal clear and not only do they redirect light but they are also a lens designed not to difuse light but redirect it.
Trev
Well, I am pretty proud I started this thread now.
I did trash my lcd by breaking it as pealing the last layers but as sad as I am of losing $450 and Alan sending me 2 scratched split fresnels I will probably try again with another since it was kind of fun and its still cheaper now than buying a commercial projector at this point.
I tested the fresnels and lens triplet quite a bit with just a transparent image and it seemed impossible to focus the entire image with the image before both fresnels. I came to the conclusion that the problem is the FL of the lens triplet and FL of the fresnels combination. The triplet only wanted to focus on things that are about 13 inches behind it but if I placed the fresnels behind the image plane the fresnels projected the barrel of the lens on the screen. Looks like I needed a shorter FL triplet for the same fresnels or different FL fresnels for the same triplet.
What blows my mind is that Alans site design shows placing the original unsplit fresnel before the lcd and condensing the light through the lcd and to the triplet. Well this does not work either. I tried placing the fresnels together as before split before the lcd and this came to the same problem. Projecting the lens.
btw, since I was desperate to get some big screen action I tried the 100 inch big screen ebay scam idea with the fresnels. Well its crap but then I tried holding the triplet infront of the 20 inch tv. Huge difference. It was very sharp. Still dark and darker on the edges but much much sharper than the fresnels.
My fresnels were 8.9 and 13 inches and the triplet 13 inches. I could not get this to work with both fresnels before the lcd. Tried and tried. No frigin way.... Image was show in the middle of the lens barrel along with it on the screen.
I did trash my lcd by breaking it as pealing the last layers but as sad as I am of losing $450 and Alan sending me 2 scratched split fresnels I will probably try again with another since it was kind of fun and its still cheaper now than buying a commercial projector at this point.
I tested the fresnels and lens triplet quite a bit with just a transparent image and it seemed impossible to focus the entire image with the image before both fresnels. I came to the conclusion that the problem is the FL of the lens triplet and FL of the fresnels combination. The triplet only wanted to focus on things that are about 13 inches behind it but if I placed the fresnels behind the image plane the fresnels projected the barrel of the lens on the screen. Looks like I needed a shorter FL triplet for the same fresnels or different FL fresnels for the same triplet.
What blows my mind is that Alans site design shows placing the original unsplit fresnel before the lcd and condensing the light through the lcd and to the triplet. Well this does not work either. I tried placing the fresnels together as before split before the lcd and this came to the same problem. Projecting the lens.
btw, since I was desperate to get some big screen action I tried the 100 inch big screen ebay scam idea with the fresnels. Well its crap but then I tried holding the triplet infront of the 20 inch tv. Huge difference. It was very sharp. Still dark and darker on the edges but much much sharper than the fresnels.
My fresnels were 8.9 and 13 inches and the triplet 13 inches. I could not get this to work with both fresnels before the lcd. Tried and tried. No frigin way.... Image was show in the middle of the lens barrel along with it on the screen.
Yes the polarizers came off. Not sure if you remember I said I saw some stains that were permanent. They werent stains. They were cracks in the actual lcd. I think this happened when I was popping open the plastic cover off the front but not really sure . I just wasnt gentle enough by using a small screw driver etc. I was anxious and I now I gotta pay. The lcd was working fine except the left and right side could not be used for a clean image. A few days ago I realized my lamp was not putting an image through this lcd at all so I figured that cant be right and looked at the lcd layers again. Sure enough there was one more polarizer off the front that needed to be removed. The lcd got more fragile now as you can imagine. Still I saw yet another layer of thin plastic so I started removing that. It was trasparent and it was the final layer before the lcd but was not necessary since it was fairly clear but kept going since I already started. Well, these sheets are pretty hard to remove. They are really stuck there and I had a person helping me but I pulled a little to hard, slipped and the sheet tore into the ribbon board or controller cables. Actually as I was removing this last layer the lcd glass was already starting to come apart even more so this was where I really screwed up.
But had I just been more calm and carefull at the beginning everything would have been fine.
As I was removing the polarizers I was thinking, there has got to be a safer way to remove these. Maybe by applying a liquid , alcohol to ease the glue separation. I was putting a lot of force to pull these polarizers. If you are not carefull you can crack your glass this way too or slip and rip .
But had I just been more calm and carefull at the beginning everything would have been fine.
As I was removing the polarizers I was thinking, there has got to be a safer way to remove these. Maybe by applying a liquid , alcohol to ease the glue separation. I was putting a lot of force to pull these polarizers. If you are not carefull you can crack your glass this way too or slip and rip .
rules
Cruser, The 'rules' are everywhere...almost everything I've read about the fresnel states the limitations..
An example:
A partial solution to the dimness is to use a larger lens to focus more of the available light. But size comes with a price. The weight of a lens increases as the cube of its diameter. So, if you want to use a lens ten times bigger across, it will weigh a thousand times as much. Fortunately, this weight issue was solved by a guy named A. J. Fresnel with a special reduction program for overweight lenses. This program scrunches the lens down, almost flattening it out.... Unfortunately, the Fresnel reducing process also slightly reduces the lens' ability to present you with a perfect image...
Fresnel lenses show up all over the place where large, lightweight lenses are needed and optical perfection is not.
Cruser, The 'rules' are everywhere...almost everything I've read about the fresnel states the limitations..
An example:
A partial solution to the dimness is to use a larger lens to focus more of the available light. But size comes with a price. The weight of a lens increases as the cube of its diameter. So, if you want to use a lens ten times bigger across, it will weigh a thousand times as much. Fortunately, this weight issue was solved by a guy named A. J. Fresnel with a special reduction program for overweight lenses. This program scrunches the lens down, almost flattening it out.... Unfortunately, the Fresnel reducing process also slightly reduces the lens' ability to present you with a perfect image...
Fresnel lenses show up all over the place where large, lightweight lenses are needed and optical perfection is not.
Attachments
Re: brainchild
Never said I had bad results, I just saw fresnel artifacting in my text. I've spent days arranging my optics in myriad configurations and have tried the fres up front many times at the 2" sweet spot and greater/lessor distances (for the sake of research). I had always planned on keeping the fres in back anyway because it simply stands to reason; you can't make a spherical surface two dimensional without the sphere becoming 'fractured', (imagine how you'd have to cut a paper 1/2 sphere to make it lay flat). I noticed a tiny increase in brightness with the fres up front, but no more 'even lighting' whatsoever. The brightness increase was so negligible that I don't even factor it as a consideration. Another big disadvantage to using the fres up front is that you'll have to increase your enclosure length by another 2 inches.
ace3000_1 said:
Never said I had bad results, I just saw fresnel artifacting in my text. I've spent days arranging my optics in myriad configurations and have tried the fres up front many times at the 2" sweet spot and greater/lessor distances (for the sake of research). I had always planned on keeping the fres in back anyway because it simply stands to reason; you can't make a spherical surface two dimensional without the sphere becoming 'fractured', (imagine how you'd have to cut a paper 1/2 sphere to make it lay flat). I noticed a tiny increase in brightness with the fres up front, but no more 'even lighting' whatsoever. The brightness increase was so negligible that I don't even factor it as a consideration. Another big disadvantage to using the fres up front is that you'll have to increase your enclosure length by another 2 inches.
you may also want to look in a scientific optics catalogue, some chrome tupperware shops etc to obtain a palm sized bowl of glass that can reflect the light well. say if you bong is well coated with thc even that might work. this goes under the hps mh bulb.
about the rings, after being really confused about his thread for a while, i have raised the lcd panel half an inch from the original dry wipe ohp glass and the lines are completely obliviated = superb display, and still as well as a the zeiss (almost) lens and mirror jobby can focus. wikked
i love my ohp
about the rings, after being really confused about his thread for a while, i have raised the lcd panel half an inch from the original dry wipe ohp glass and the lines are completely obliviated = superb display, and still as well as a the zeiss (almost) lens and mirror jobby can focus. wikked
i love my ohp
brainchild
yeah thats weired crusuer and a few others seem to get thiers going ok or working fine, the infocus i got here works fine with it maybe its your frensels, who know's, but i think alot of arguments start in here as we are all not using the exact same gear, if we was asuming also using the same panel, light source, reflector ect there still could be different resalts being in the diferent building materials and constrution acheived by each of us, so realy to me this seeems like abit of a hit and miss situation, from memory your frensel is from china and not diylab's, maybe thats the problem, as for me well i use the single frensel method for now, ill try the double method later cos it does make one hell of a difference when set up corectly but ill fool with it abit latter on when i have abit more time, finding some nice and well matched frensels with good focals is the hard bit.
Trev
yeah thats weired crusuer and a few others seem to get thiers going ok or working fine, the infocus i got here works fine with it maybe its your frensels, who know's, but i think alot of arguments start in here as we are all not using the exact same gear, if we was asuming also using the same panel, light source, reflector ect there still could be different resalts being in the diferent building materials and constrution acheived by each of us, so realy to me this seeems like abit of a hit and miss situation, from memory your frensel is from china and not diylab's, maybe thats the problem, as for me well i use the single frensel method for now, ill try the double method later cos it does make one hell of a difference when set up corectly but ill fool with it abit latter on when i have abit more time, finding some nice and well matched frensels with good focals is the hard bit.
Trev
maybe we shoudl start a hair test... if you can see a blonde hair lying on top of the lcd then you have a good image. only head hair tho.
I am using a diylabs Fresnel that I have split and I have crispy crunchy peanut buttery clear text. I have only about an inch of space between the frensel and the lcd but I do not have any pattern’s or rings and it looks great. I can clearly see the pixels in the text when I get a few feet away from my screen and when I am in my seating area the text is great. I can understand why putting the Fresnel in the back can give the best picture but for me the price performance ratio is just two high to invest in larger more expensive lenses at this point. I think as long as you put space and keep the front Fresnel very strait you should have a very acceptable picture for a $30 Fresnel.
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