Xenotar 150 2.8 Projector Lenses

[aly324]

Do the Xenotar 150mm f/2.8 projector lenses share the same optical design with the ones meant for large format photography?

[Greg]

Thank you for posting this. Have come across quite a few large aperture projection lenses and always wondered about their projected images. FYI: Buhl large aperture projection lenses in no way project images anywheres near that of a Xenotar. The old comparing apples to oranges saying but optically speaking.

[Corran]

Are you talking about those Xenotar lenses sold years ago on eBay that were used for scientific testing? Or something like the Rollei 150mm f/2.8 projection lens or similar?

[LabRat]

Remember that many/most projection lenses (despite longer FL's) were designed with a central sharp area, usually for smaller format projection that is critically sharp, but sharpness falls off quickly in the IC... The trick is to find a lens with a good transition in between these areas...

I recommend older lenses, as they were not critically as sharp as newer ones, as the older ones blend better...

Steve K

[aly324]

I mean this lens (and variants)
https://www.bhphotovideo.com/c/produ...rojection.html

Just out of idle curiosity really. I assume they aren’t the same because otherwise someone would’ve adapted the optical cells already for photography, seeing how expensive the “real” Xenotar 150’s are.

[Greg]

I believe the lens was also marketed as a 150mm f/2.8 S-Heidosmat P66 projector lens for Rollei P66 slide projector. Projector was for projecting 2 1/4" square slides. So coverage probably around 84mm in diameter. Probably a bit less at infinity. Same formula as the "real" Xenotar 150? I'd guess yes. Possibly Bob can shed some light on this projector lens since this/my post is more of educated guesses in nature.

[Corran]

Looks the same as the Rollei Greg mentioned, but that is definitely not the same lens as the Xenotar. I have a Xenotar and my friend has a Rollei 150mm f/2.8, and they are clearly different. The Rollei definitely has less usable image circle before distortion (swirl). I assume the Rollei is closer to a Petzval design, not double-Gauss.

[Dan Fromm]

Looking at the picture of the lens in the B&H link in post #5 above makes me wonder about a purely mechanical issue. The projector lens is fixed aperture, its barrel is plastic. Is the lens made up of two cells that screw into the barrel and so might be screwed into a shutter or are the glasses mounted individually in the barrel? I've seen fixed aperture lenses whose elements were mounted individually in the barrel. Not knowing better, I've opened one. The elements all fell out.

[Bob Salomon]

Looking at the picture of the lens in the B&H link in post #5 above makes me wonder about a purely mechanical issue. The projector lens is fixed aperture, its barrel is plastic. Is the lens made up of two cells that screw into the barrel and so might be screwed into a shutter or are the glasses mounted individually in the barrel? I've seen fixed aperture lenses whose elements were mounted individually in the barrel. Not knowing better, I've opened one. The elements all fell out.

Most of the 150 Xenotars for the Rollei P66, P66S and Dual had a metal barrel, they were quite heavy. The economy lens for these projectors were a 3.5 and had a plastic barrel.

[Dan Fromm]

Bob, thanks for the correction.