hello people,
i was just wondering, i'm was planning to use a 31 x 31 cm fresnel lens on a 15" benq...how is it that people get corner to corner focus and brightness and the whole screen........
i had a warped fresnel before and it was much brighter in the middle than the corners.....i ended up smashing it to pieces 'cos it was no good! but the corners were cut (vario focal triplet 3m ohp) but my fresnel was unsplit.
can someone please help me on these 2 things
1. perfect (well, almost) brightness and the whole screen
2. i have looked but results were confusing, the benefits of whole and split fresnel..
i guess only pj masters can answer these fully.....ace where are u man??????
thanx
i was just wondering, i'm was planning to use a 31 x 31 cm fresnel lens on a 15" benq...how is it that people get corner to corner focus and brightness and the whole screen........
i had a warped fresnel before and it was much brighter in the middle than the corners.....i ended up smashing it to pieces 'cos it was no good! but the corners were cut (vario focal triplet 3m ohp) but my fresnel was unsplit.
can someone please help me on these 2 things
1. perfect (well, almost) brightness and the whole screen
2. i have looked but results were confusing, the benefits of whole and split fresnel..
i guess only pj masters can answer these fully.....ace where are u man??????
thanxHi DJ,
Selection of projection lens is more important than I originally thought, I've since discovered after flattening fresnels reliably that my 80mm triplet (very common, 330mm FL from DPC) cannot quite manage perfect corner to corner focus on my 15" BenQ.
My sketchy understanding of it is that this could be rectified using a projection lens with larger FOV angle, or by increasing the FL of the front fresnel component. Please correct me fellas if I've got it all wrong 😉
Personally I can put up with a little bluring at the edges and won't entertain the idea of longer 'pro' fresnels for box size reasons.
As for split vs unsplit, I can't comment on the quality issues as I haven't tried both. It's suggested unsplit will result in better quality image, but lacks ability to correct for keystone.
Selection of projection lens is more important than I originally thought, I've since discovered after flattening fresnels reliably that my 80mm triplet (very common, 330mm FL from DPC) cannot quite manage perfect corner to corner focus on my 15" BenQ.
My sketchy understanding of it is that this could be rectified using a projection lens with larger FOV angle, or by increasing the FL of the front fresnel component. Please correct me fellas if I've got it all wrong 😉
Personally I can put up with a little bluring at the edges and won't entertain the idea of longer 'pro' fresnels for box size reasons.
As for split vs unsplit, I can't comment on the quality issues as I haven't tried both. It's suggested unsplit will result in better quality image, but lacks ability to correct for keystone.
dpc??? where and what is that?? thanx for the input though!! i've got a vario focal triplet from 3m ohp the corners do seem a little blurry but i thought that, that had to do with my fresnel lens being too small... when i moved the fresnel lens about the corners seemed fine!!!
but i've seem many peoples pjs with good results with similar triplet and 31 cm (standard) fresnel..... but i'm only using a 150w hqi (very bright!) and my test results were very good! i've had to opt for the larger fresnel from 3dlens.....
still need info...thnx 
but i've seem many peoples pjs with good results with similar triplet and 31 cm (standard) fresnel..... but i'm only using a 150w hqi (very bright!) and my test results were very good! i've had to opt for the larger fresnel from 3dlens.....
still need info...thnx
Whoa smiley overload 
😀
DPC = www.diyprojectorcompany.com - I got the 15" x 15" fresnels (38cm x 38cm), they were huge before the dremel got some action
Perhaps someone else can shed some light (shoot me now😉) on the lens issue.
EDIT: Forgot to say I believe my corner focus problem may be to do with a slightly mismatched condensor lens, so don't rely on my experience/comments fully, get some more input!
😀 DPC = www.diyprojectorcompany.com - I got the 15" x 15" fresnels (38cm x 38cm), they were huge before the dremel got some action
Perhaps someone else can shed some light (shoot me now😉) on the lens issue.
EDIT: Forgot to say I believe my corner focus problem may be to do with a slightly mismatched condensor lens, so don't rely on my experience/comments fully, get some more input!
did you have to pay import duty on that lens you ordered from diyprojectorcompany????
normally when you order lens from the same company they come matched!!!!!!!!!????!!!!!!
i think my triplet is o.k for focusing just need a better fresnel...well i wait until i get bigger fresnel then i will mess around with triplet...it did come from a very expensive 3m ohp that almost had a 15" area!!!!!! so based on that its got potential!
making sure everything is centred is the hard part
normally when you order lens from the same company they come matched!!!!!!!!!????!!!!!!
i think my triplet is o.k for focusing just need a better fresnel...well i wait until i get bigger fresnel then i will mess around with triplet...it did come from a very expensive 3m ohp that almost had a 15" area!!!!!! so based on that its got potential!
making sure everything is centred is the hard part
Quin said:
A larger field angle projection lens will capture (and so project) more lcd focused area, but a larger focal field fresnell will do nothing if the field angle of the projection lens is too small. The field fresnell should have the focal lenght neccesary so the light is condensed on the optical center of the projection lens (moreless at the center of the lens).
thanks rox. i kinda knew it was the fresnel lens...as you said the angle was too small to strow light overthe whole screen.. i just placed order for larger fresnel.....my results are going to be sickkkkkkkkkkkkk...pics WILL be posted asap. no longer than 2 weeks!!!!!!!!! can't wait..my 5.6" shoulde be finished at that time also.....
i could still do with more info...i love knowing stuff u know what i mean about knowing the know how stuff..you know?? 
🤐 
i could still do with more info...i love knowing stuff u know what i mean about knowing the know how stuff..you know??
🤐 DJ,
I did have to pay hefty import duties unfortunately, but you could try your luck getting it sent by Airmail instead of a courier, you may get away with it then (50/50 chance from what I hear).
Rox,
Thank you for helping my understanding - I guess I am thinking the wrong way. If you look at my diagram, isn't the angle smaller with the longer focal length front fresnel? So if you used the same projection lens in both setups, you might find it could cope with the FOV better with a longer FL fresnel than with the short fresnel FL?
Where am I going wrong?
I did have to pay hefty import duties unfortunately, but you could try your luck getting it sent by Airmail instead of a courier, you may get away with it then (50/50 chance from what I hear).
Rox,
Thank you for helping my understanding - I guess I am thinking the wrong way. If you look at my diagram, isn't the angle smaller with the longer focal length front fresnel? So if you used the same projection lens in both setups, you might find it could cope with the FOV better with a longer FL fresnel than with the short fresnel FL?
An externally hosted image should be here but it was not working when we last tested it.
Where am I going wrong?
how much did you have to pay quin and what did you order..thanx
i am getting it airmail!!!!!
my understanding of the whole picture issue is this.... the fresnel is slightly smaller than the lcd but it bends the light at and angle that dosen't reach the edges so when the lens picks it up it comes up dim and blurry or out of focus 'cos it was never in focus due to fresnel...i hope i'm right if not sue me 'cos i thin ki'm right!!
i am getting it airmail!!!!!
my understanding of the whole picture issue is this.... the fresnel is slightly smaller than the lcd but it bends the light at and angle that dosen't reach the edges so when the lens picks it up it comes up dim and blurry or out of focus 'cos it was never in focus due to fresnel...i hope i'm right if not sue me 'cos i thin ki'm right!!
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Yeah, not the same thing I was going on about, but sure that'll definitly cause a problem for you.
Give me a moment, I'll try and find a list of what I ordered.
Give me a moment, I'll try and find a list of what I ordered.
1 x Front Surface Mirror (FS) $7.50
1 x Light Source Upgrade Kit $19.99
1 x Complete Lens Kit $69.99
1 x 60mm Condenser Lens $12.99
1 x 250w HQI Metal Halide Kit
- Voltage: 210-240v $159.95
Shipping was £30, I got hit for a further £30 on duties 🙁
Here's a shot I took of it in action the other night, I finally coaxed a half decent shot out of my naff camera. Image size was ~6foot, the screen was creme wallpaper - I've yet to sort out a permanent white screen, it makes such a huge difference to brightness/colours. Check the corners out, definitly a little fuzzy.
The Barrel distortion (think thats the right term, aka banana screen 😉) and the darker corners are products of the camera, can't see it in real life.
1 x Light Source Upgrade Kit $19.99
1 x Complete Lens Kit $69.99
1 x 60mm Condenser Lens $12.99
1 x 250w HQI Metal Halide Kit
- Voltage: 210-240v $159.95
Shipping was £30, I got hit for a further £30 on duties 🙁
Here's a shot I took of it in action the other night, I finally coaxed a half decent shot out of my naff camera. Image size was ~6foot, the screen was creme wallpaper - I've yet to sort out a permanent white screen, it makes such a huge difference to brightness/colours. Check the corners out, definitly a little fuzzy.
An externally hosted image should be here but it was not working when we last tested it.
The Barrel distortion (think thats the right term, aka banana screen 😉) and the darker corners are products of the camera, can't see it in real life.
dude you smashed it and your complaining?!??!?!?!?!??!!
if only 1 side of your screen is fuzzy thats to do with your lens not being centred. you have to align everything centre to get a perfect focus. if both of your sides are fuzzy then that has got to do with the fact that the lens you are using to focus is too small and not all the light from the edges are passing throught the lens if u move it further up it will be completely out of focus......IF i'm right the only solution is new focus lens or try adjusing your fresnel above the lcd try tilting and moving back and forth and moving your focus lens (i know what your thinking, i aint got 5 hands!!)
either way great results dude......and £30 for import is cool dude even though you werent expecting it....try £55 for something half the size and weight from japan!!!!!!!!! 🙁
if only 1 side of your screen is fuzzy thats to do with your lens not being centred. you have to align everything centre to get a perfect focus. if both of your sides are fuzzy then that has got to do with the fact that the lens you are using to focus is too small and not all the light from the edges are passing throught the lens if u move it further up it will be completely out of focus......IF i'm right the only solution is new focus lens or try adjusing your fresnel above the lcd try tilting and moving back and forth and moving your focus lens (i know what your thinking, i aint got 5 hands!!)
either way great results dude......and £30 for import is cool dude even though you werent expecting it....try £55 for something half the size and weight from japan!!!!!!!!! 🙁
Quin said:Rox,
Thank you for helping my understanding - I guess I am thinking the wrong way. If you look at my diagram, isn't the angle smaller with the longer focal length front fresnel? So if you used the same projection lens in both setups, you might find it could cope with the FOV better with a longer FL fresnel than with the short fresnel FL?
An externally hosted image should be here but it was not working when we last tested it.
Where am I going wrong?
You can't use the same projection lens on this two so differnt setups; the second setup would give you a VERY SMALL IMAGE.
You first of all have to see what throw you got and then you can work out what is the separation from lcd to triplet (THERE IS ONLY 1 FOR EACH THROW). Then the last thing you have to do is work out the fresnell focal so the light enters the triplet. (you wont have the exact focal available for your setup but you can buy the closest and then adjust it to your setup MOVING THE LAMP the light cone moves on the triplete side as well so you are able to have any virtual focal point in a aceptable range. (a very good friend of mine has very good results using this tecnic with 330 field fresnell when he should use close to 600mm fresnell.
can someone PLEASE tell me te difference between split and unspit fresnel!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!🙁 🙁 🙁 🙁 🙁 🙁 🙁 🙁 🙁 🙁
split fresnell is when you have the lcd between two fresnells.
Unsplit is when you have two fresnells behind the lcd.
split; you can do keystone tilting the front fresnell, and the birightness will increase on corners, but the image cuality will be less sharp because the fresnell will brlurr the image.
Unsplit is when you have two fresnells behind the lcd.
split; you can do keystone tilting the front fresnell, and the birightness will increase on corners, but the image cuality will be less sharp because the fresnell will brlurr the image.
so the image with un-split fresnel will be sharper but less bright corner to corer?????
but i'm using unsplit and its very bright!!!!!! on a 150 hqi!!!??!!!
i just ordered a large fresnel from 3dlens i was planing on unsplit will corners still be dim????
what about the colour?????
also if your focusing with unsplit the image will be clear, with split fresnel you will be focusing on a lens hat MUST affect the quality dramitically not just sharpness!!!!?????!!???? your focusing on plasic lens instead of a lcd screen!!!please comment
thanx in advance!
but i'm using unsplit and its very bright!!!!!! on a 150 hqi!!!??!!!
i just ordered a large fresnel from 3dlens i was planing on unsplit will corners still be dim????
what about the colour?????
also if your focusing with unsplit the image will be clear, with split fresnel you will be focusing on a lens hat MUST affect the quality dramitically not just sharpness!!!!?????!!???? your focusing on plasic lens instead of a lcd screen!!!please comment
thanx in advance!
yes, since you got a fresnell lens in the image way, it afect the cuality.
About the image becoming dimer when unsplit, i would say it depends on some factors; tft vision angle, lcd size, projection lens focal (cos if you have a large focal the triplet needs to be placed farther from the lcd so the light angle from the fresenlls hitting the lcd is more parallel than if you had a close triplet, that would require very strong angle on the corners of the lcd so the light would decrease).
if you have 135 tirplet and 15" and would like 100" image (suppose it works fine, thats another story about the FOV of this lens....) then you need to place at 51cm from the lcd and this will give you 17 degrees angle on the critical corner, this is not too much angle, the lcds have a vision angle of 120 degrees and more so 15 degrees would not be noticed at all.
About the image becoming dimer when unsplit, i would say it depends on some factors; tft vision angle, lcd size, projection lens focal (cos if you have a large focal the triplet needs to be placed farther from the lcd so the light angle from the fresenlls hitting the lcd is more parallel than if you had a close triplet, that would require very strong angle on the corners of the lcd so the light would decrease).
if you have 135 tirplet and 15" and would like 100" image (suppose it works fine, thats another story about the FOV of this lens....) then you need to place at 51cm from the lcd and this will give you 17 degrees angle on the critical corner, this is not too much angle, the lcds have a vision angle of 120 degrees and more so 15 degrees would not be noticed at all.
dude you confusing the helllllll out of me!!! and your diffcult to understand! 🙂
all i'm saying with my triplet and my 31cm unsplit fresnel the picture was super bright and super crisp!!!! i had a 100" or something like that image from about 2.5 m.
but the corners were cut and fuzzy. i think that was due to my fresnel!!
i have just ordered large fresnel.. i will have a finished pj by this weekend 6 days..trust will post results!! 
all i'm saying with my triplet and my 31cm unsplit fresnel the picture was super bright and super crisp!!!! i had a 100" or something like that image from about 2.5 m.
but the corners were cut and fuzzy. i think that was due to my fresnel!!
i have just ordered large fresnel.. i will have a finished pj by this weekend 6 days..trust will post results!!
sorry, i am speaking in other language than my tounge language 😀
what have you ordered? a large frenslnell form 3dlens, you mean 15" side but 330/220 focal fresnells? that will give you more area but the luminosity and focus will be exactly the same on the area of 31 x 31 330/220 fresnells.
if you have problems with your lcd if it does not fit the current fresnells, then you have done ok but if you are triying to increase brighness with those large fresnells they wont help you becaouse they have the same focal.
what have you ordered? a large frenslnell form 3dlens, you mean 15" side but 330/220 focal fresnells? that will give you more area but the luminosity and focus will be exactly the same on the area of 31 x 31 330/220 fresnells.
if you have problems with your lcd if it does not fit the current fresnells, then you have done ok but if you are triying to increase brighness with those large fresnells they wont help you becaouse they have the same focal.
english is my third language!!!
it is the bigger area that i require if u look at the pic below that was my problem........but my new lens will be great !!!! i have also ordered smaller fresnel and smaller focal triplet from my 5.6" screen. so i will have 2 pj finished by this weekend!!!
i will be selling both for a good price!
i'm going to be mass producing 15" benq with 250 hqi and selling them by the gallons mate......if there money top be made i'm making it!!!...if there women to be laid i'm laying them!!??!! u get the idea..
it is the bigger area that i require if u look at the pic below that was my problem........but my new lens will be great !!!! i have also ordered smaller fresnel and smaller focal triplet from my 5.6" screen. so i will have 2 pj finished by this weekend!!!
i will be selling both for a good price!
i'm going to be mass producing 15" benq with 250 hqi and selling them by the gallons mate......if there money top be made i'm making it!!!...if there women to be laid i'm laying them!!??!! u get the idea..
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