LCD Projector lens as large format camera lens

BySumbergsStache · Apr 24, 2016

I was just setting up the projector at church when I had a thought, could the lens from a LCD projector be successfully used in a large format camera?

I don't actually have one, but if the idea had promise I'd see if I could get a junker from school or goodwill

pdeeh · Apr 24, 2016

Plenty of people use projector lenses for LF, though whether anybody does exactly what you are proposing I've no idea (i.e. using a lens from a digital projector)
If you can find one for little or no money, there's no reason not to give it a try.
Report back if you do though

Luckless · Apr 24, 2016

Very much a 'maybe' sort of thing, especially if you're aiming for large format. Most modern projectors, especially cheap consumer ones, use very small LCD screens internally, so I suspect that you may have issues getting suitable coverage. However if you don't really care too much about the edges, then I would rate it 'probably viable' if you're willing to do some work to refit a lens out of a random unknown projector.

Rigging up some manner of camera obscura to test lenses is probably your best starting point on a project like this. And I do hope you can document it.

Whether or not you really save anything is another important question, but where is the fun in just buying something off the shelf when you could explore and build things?

Kilgallb · May 1, 2016

LCD projectors use a telecentric lens which means the imager effectively only focuses at infinity. No this will not work. The lens is built for an image that is usually 25 mm to 10 mm diagonal.

BySumbergsStache · May 15, 2016

Huh... that's really interesting info Kilgallb. What about a traditional overhead projector lens?

John Ellis · Jun 23, 2021

Like others pointed out, with your telecentric system, the angle of incidence of light illuminating the object is constant which in return creates a more uniform brightness on the image. They can be designed with a variable offset (from 0% - 130%). The illumination system can be independent from the projection lens, so it’s possible to exchange one without modifying the other. As a drawback, they tend to be more expensive and include more elements than a non-telecentric system

In a non-telecentric system the illumination is not constant and it’s usually at an offset angle, so the brightness on the image also is affected by this. They tend to have a lower cost than a telecentric system, but they have more limitations on their design, as an example all non-telecentric systems have to have a fixed offset.

Hope this helps. More in depth discussion here
https://www.opticsforhire.com/blog/projection-lens-design

John and Victor

wiltw · Jun 23, 2021

One thing to consider about repurposing ANY lens which is not intially designed for Large Format film...HOW do you have a SHUTTER to control exposure? And even if your camera has a focal plane shutter, HOW do have a controllable APERTURE whicn can be made large/smaller as indicated by your exposure meter?

AgX · Jun 23, 2021

John Ellis said:
Like others pointed out, with your telecentric system, the angle of incidence of light illuminating the object is constant which in return creates a more uniform brightness on the image.

Being telecentric in your reference refers to the illuminating optics, not the imaging optics (the projection lens).
https://images.squarespace-cdn.com/...E9UQV1MFTN1JX61/illumination.png?format=1000w

ic-racer · Jun 23, 2021

LCD Projector lens as large format camera lens

Large format?? Looks smaller than 35mm format to me. Maybe You have a lens form some monster projector for a movie theater or something that has a massive 0.95" chip. Still far from large format. (0.95" = 24mm)

rknewcomb · Jun 23, 2021

I put one of these Beseler projection lenses on an 8x10 camera before and it seem to cover. Very fast lens so depth of field was very thin. I only tried for the heck of it and never made any pictures with it.
https://www.ebay.com/itm/202681026448?hash=item2f30bb0790:g:Sh0AAOSwBfRc3Zq8
Robert

bdial · Jun 24, 2021

wiltw said:
One thing to consider about repurposing ANY lens which is not intially designed for Large Format film...HOW do you have a SHUTTER to control exposure? And even if your camera has a focal plane shutter, HOW do have a controllable APERTURE whicn can be made large/smaller as indicated by your exposure meter?

Often the point of using some these “alt” lenses is to exploit the softness or shallow DOF you would get working wide open. But that does lead to challenges if you need a short exposure time, and you aren’t working with a camera that has a shutter. For aperture, it is possible to make Waterhouse style aperture stops. I have a projection Petzval that someone before me soldered a big washer into the middle to stop it down some.

John Ellis · Jun 24, 2021

AgX said:
Being telecentric in your reference refers to the illuminating optics, not the imaging optics (the projection lens).
https://images.squarespace-cdn.com/...E9UQV1MFTN1JX61/illumination.png?format=1000w

Thanks for the note. You are right; a better schematic is covered here.
https://www.opticsforhire.com/blog/telecentric-lenses-design?rq=telecentric

John and Victor

AgX · Jun 24, 2021

So, now you are speaking of the projection lens. However a telecentric screen projection lens makes no sense.

Kilgallb · Jun 27, 2021

Makes perfect sense in an LCD projector. The light source travels from behind the LCD array and emerges more or less in parallel from each element.

The front elements spread the lift rays to enlarge the image.

AgX · Jun 27, 2021

For a telecentric projectiom lens to work the rays coming from such a illumination set-up as you describe ALL rays must be exactly parallel otherwise not only illumination effeciency may get lost but also part of the image.

LCD Projector lens as large format camera lens

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