YES IT WOULD BE! ive been searching all over lol. I even asked if theres any projection panels that have a 5" window, simply because theyre better resoloution.
Would adding one of these lenses screw up the light output?
Would adding one of these lenses screw up the light output?
lens extender
>Would adding one of these lenses screw up the light output?
It would not hurt the brightness, if you used fresnels to focus the light into the center of the negative lens. But it might introduce some of everything: Spherical aberration, chromatic aberration, barrel or pincushion distortion.
I think it is worth having a look at, though. I have a few of surplus shed's big negative lenses. I will see if I can get one of the big CRT lenses cheap on eBay to run an experiment.
Unless somebody has a big CRT lens just gathering dust, that they want to lend me for a while?
>Would adding one of these lenses screw up the light output?
It would not hurt the brightness, if you used fresnels to focus the light into the center of the negative lens. But it might introduce some of everything: Spherical aberration, chromatic aberration, barrel or pincushion distortion.
I think it is worth having a look at, though. I have a few of surplus shed's big negative lenses. I will see if I can get one of the big CRT lenses cheap on eBay to run an experiment.
Unless somebody has a big CRT lens just gathering dust, that they want to lend me for a while?
Re: lens extender
Guy, Ive got a Delta HD-8 REV. B sitting here. It's big and heavy. I'll find out first what the shipping charges will be to get it there.Guy Grotke said:
how different are RPTV lenses to CRT projector lenses? i just wont my ebay lens. ill be hella PO'd if i coulda used a 7" or 8" CRT projector lens. Meh oh well ive and learn. I plan on selling a few projectors anyways.
Just got one
Mikey_p: No need, I just got a 5" diameter lens on eBay pretty cheap.
CRT versus RPTV: I guess this depends on the video source. If the RPTV is CRT-based, then I would bet it is very similar to a CRT front projector lens. Maybe the focal length is even shorter, since the screen would be closer in an RPTV.
Lenses for CRTs have to be very large, so they can collect enough of the diffuse light that goes in all directions from a CRT pixel. That's also why they have such short focal lengths, so they are placed very close to the CRT.
Lenses for LCD projectors can be smaller if a light condensing system is used.
Mikey_p: No need, I just got a 5" diameter lens on eBay pretty cheap.
CRT versus RPTV: I guess this depends on the video source. If the RPTV is CRT-based, then I would bet it is very similar to a CRT front projector lens. Maybe the focal length is even shorter, since the screen would be closer in an RPTV.
Lenses for CRTs have to be very large, so they can collect enough of the diffuse light that goes in all directions from a CRT pixel. That's also why they have such short focal lengths, so they are placed very close to the CRT.
Lenses for LCD projectors can be smaller if a light condensing system is used.
Been there, done that, got the T-shirt and bobblehead.
I tried a good 5" negative lens with a big heavy 6" crt lens. Yes it does project but its not as fast as a 60mm triplet or 80mm duplet. I didnt crowbar it into my projector or funnel light into it with a fresnel though.
My test was go 10ft from a 19" monitor and project in a dark room to a wall a few feet further. The image is small but with the same parameters you can test lenses relative to each other and try combinations quickly.
My ohp lens btw is 2x as bright as the 60mm fujinon-xerox triplet.
I tried a good 5" negative lens with a big heavy 6" crt lens. Yes it does project but its not as fast as a 60mm triplet or 80mm duplet. I didnt crowbar it into my projector or funnel light into it with a fresnel though.
My test was go 10ft from a 19" monitor and project in a dark room to a wall a few feet further. The image is small but with the same parameters you can test lenses relative to each other and try combinations quickly.
My ohp lens btw is 2x as bright as the 60mm fujinon-xerox triplet.
experiment
I was thinking of adding the negative lens to see if I could get reasonable performance from a CRT lens with a larger LCD. There seem to be a lot more 4" and 5" CRT lenses around at very low cost, compared to 8" CRT lenses that could work with a 7" Lilliput monitor LCD.
I don't have a Lilliput, but I can fake it with a calibrated color pattern printed on a piece of transparency film.
I was thinking of adding the negative lens to see if I could get reasonable performance from a CRT lens with a larger LCD. There seem to be a lot more 4" and 5" CRT lenses around at very low cost, compared to 8" CRT lenses that could work with a 7" Lilliput monitor LCD.
I don't have a Lilliput, but I can fake it with a calibrated color pattern printed on a piece of transparency film.
DAMMIT! someone sniped my lens! ugh! i wonder if i can go garbage picking tonight. thats a real downer
Garbage picking? You think your neighbors will have these with their trash? lol 😉
goto surplus shed. i think its the tv projection lens. good luck using it.
big screen tvs are quite common here. I have no problem lugging one home just to dysect it.
however i am getting impatient and ill probably just take your advice.
however i am getting impatient and ill probably just take your advice.
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