Could a 135mm enlarger lens be adapted for use on a MF projector?

[68degrees]

I need a short lens for my MF (6x6,6x9)projecter. It currently has a 300mm lens which makes the projected image too small in a small room. Is it possible to take a 135mm enlarger lens and make an adapter for the projector?

 

[sevo]

It depends on the projector and the degree of hacking you are ready to perform on it, as it may amount to sawing off the front of the projector.

135mm is rather on the short side by medium format projection standards, the regular definition of a projection "normal" focal length is the double diagonal (210mm in the case of 6x9). And as most old projectors weren't intended to take lenses significantly wider than normal, it may be hard or even impossible to attach the lens to a existing projector lens barrel the DIY way, and you may have to replace the entire mounting and focusing mechanism unless you want so shell out significant amounts of money for a professional lens remounting job.

 

[Particular]

The problem I foresee is that the condensers of the projector may not be suitable for the 135mm lens. In enlargers and projectors the condensers need to be matched to the lens focal length, or else you will get uneven illumination. I once found a leitz 50mm projection lens that I thought I could use on my leitz projector to get a nice big image. The lens fit, but the projected image was useless. Bright in the center with severe fall off. It didn't even reach the corners.
Perhaps you should just try to mock it up with a cardboard tube and some masking tape. You will find out pretty soon if there is potential or not.

 

[Dwig]

In addition to the cautions already mentioned, it should be noted that an enlarging lens is designed for flat field projection at relatively close distances, much like a true macro lens. When projecting across a room, it may not deliver the edge performance desired. A regular camera lens may work better as they are designed for more distant work.

 

[sevo]

The problem I foresee is that the condensers of the projector may not be suitable for the 135mm lens. In enlargers and projectors the condensers need to be matched to the lens focal length, or else you will get uneven illumination.

Condenser lenses can often be rearranged (flipping front and back or changing spacing by inserting them in different slots) within the range the projector - but as I said, 135mm may be out of range.

 

[68degrees]

Condenser lenses can often be rearranged (flipping front and back or changing spacing by inserting them in different slots) within the range the projector - but as I said, 135mm may be out of range.

there is a 165mm lens in existence but I simply cant find one. Even in case I found one, I dont know if a different condenser is required. I will look inside and see if there is different slots to put the condensor lens. That was a great suggestion as well as the cardboard tube mockup.

 

[68degrees]

... by medium format projection standards, the regular definition of a projection "normal" focal length is the double diagonal (210mm in the case of 6x9).

does this standard apply to enlargers as well because Ive seen 105mm as the standard lens for 6x9 enlargement. Why is it different for projectors?

 

[sevo]

does this standard apply to enlargers as well because Ive seen 105mm as the standard lens for 6x9 enlargement. Why is it different for projectors?

Probably half a matter of theatres and lecture halls projecting across the long axis and for the other half a relic from the long era when Petzval type lenses with their limited angle of coverage were the only fast (as in f/2.8 and up) projection lenses.

 

[68degrees]

There are 3 lenses in the condenser assembly. There dont appear to be any empty slots. There are two latches that hold the assembly in so it can be lifted out as one unit. Probably there were different ones that could be used depending on the setup.