~50mm Slide Projector lens

[Ivo Stunga]

Hello!
I love screen-filling slide projection - they just sing heavenly hymns when using quality lens in a light-controlled room. But there's a catch - my room is small and to fill the vinyl screen (~1.8m wide) from mere ~3m... I'm forced to look for ~50mm projection lens.

Thus far I've tried:
- Meridian PC 45mm f/2.8 MC - my current lens and a tad too wide for my current room (just moved) and I'm not overly happy with the loss of edge sharpness
- Leitz Vario Elmaron f/3,5 60-110mm - a tad too narrow and suffers from pincussion/barrel distortion that I'm simply not happy with
- Native Soviet Triplet lenses just under 100mm - better not to mention these out of respect towards my slides
- Leitz Pradovit lens under 100mm - not impressed and small picture
- LETI 60-M f/2 92mm - best one I've handled so far - bright, expressive and sharp image from edge to edge, but the image is way too small :/


So, the questions are:
1) Can you please point me towards a good ~50mm prime with 42mm mount - does one exist?
2) DIY - can one install an aperture inside a given lens in hopes to improve edge sharpness? If yes, where in the lens body should I put it and from what material?

 

[koraks]

Have you considered using a taking lens and simply stopping it down to 2.8 or so? A 50mm f/2 or so should be easy to find in M42, no?

 

[Chan Tran]

Which projector that takes 42mm screw mount lens? I have a 50mm f/2.8 projection lens for the Kodak Ektagraphic projector.

 

[Ivo Stunga]

Have you considered using a taking lens and simply stopping it down to 2.8 or so? A 50mm f/2 or so should be easy to find in M42, no?

I have, yes!
Tried to fit a soviet rangefinder lens Industar 61LD, but the lens holder design is in the way - it's possible to put the lens inside and get image going on, but the result is such that the lens sits deep inside the projector/holder and creates a strong vignetting from the lens holder barrel/body. I guess this could be improved with SLR lens as the distance to focal plane is larger. Should I try small SLR lens, does such a narrow lens exist?

 

[Ivo Stunga]

Which projector that takes 42mm screw mount lens? I have a 50mm f/2.8 projection lens for the Kodak Ektagraphic projector.

In my European experience - all of them. Peleng 500AF, Peleng 500, Leitz Pradovit... 42,5mm mount to be exact.

 

[koraks]

Should I try small SLR lens, does such a narrow lens exist?

It's worth a try, but I can't tell you whether a camera lens exists that will fit in the barrel/mount of the projector. Sorry, I had not considered that limitation, but I see you've tested it already!

 

[Ivo Stunga]

Found this resource:

KX Camera Kodak Slide Projectors Since 1980 - 1732-1/2 Grand Ave. Santa Barbara, CA 93103 805-963-5625

It informs me that Rollei Projar f/2.8 50mm exists. Is it a good lens?
Says it's made in Germany by ISCO: https://deltalenses.com/product/rollei-projar-50-2-8/

 

[koraks]

I really could not say, but given this:

Bokeh Character Strong swirl.

I assume it's probably not much better in an objective sense than what you've already tried. I associate a swirly bokeh with fairly rudimentary lens designs which generally don't excel in terms of edge-to-edge sharpness, even illumination etc.

 

[Ivo Stunga]

Hmmm, interesting. It's said to have 4/2 elements - not a triplet at least!

I should test my current lens then - held in front of DSLR to see what bokeh character it provides - just for reference and insight alone

 

[Petrochemist]

In my European experience - all of them. Peleng 500AF, Peleng 500, Leitz Pradovit... 42,5mm mount to be exact.

Very odd.
Most of my projector lenses use a 2" push in mount usually with a very coarse focusing recess.

My 50mm projector is a Russian f/1.2 lens shown bellow mounted to a 52mm helicoid via a glued on stepping ring

Mounted 50mm/1.2 projector lens by Mike Kanssen, on Flickr

Sadly it doesn't cover full frame just about managing APSC, though my 40mm perspective control one has better coverage.


your 42.5mm doesn't match any thread I know, the standard 42mm ones are M42 (42x1mm) & T2 (42x0.75mm).

It seems I have a few 'projector lenses' with screw threads ~41mm being one, in total mine range from a 23.8mm diameter tube to ~60mm. I collect projection lenses to adapt & don't have much use for the projectors themselves.

 

[Ivo Stunga]

Regardless - 42mm in my case. Up to 50mm diameter can be forced inside. Forced.

My LETI 2/92 has 50mm barrel and can be forced into holder that has been cut to provide some play. Not great, but holds for sure.


So in theory I could use 50/50 and not be limited to 50/42. Hmmmmm.

So, another question:
What's a good 50mm lens with barrel size up to 50mm and how could I try one out?
I imagine that anything below 2.8 would be painful to focus with 56x enlargement.

Are enlarger lenses another viable route or are taking lenses that much better?

 

[koraks]

Are enlarger lenses another viable route?

Yeah, why not. I've got an EL-Nikkor here, 50/2.8 and that measures 47.5mm at its widest. So it should be a narrow fit.

 

[perkeleellinen]

I used to have an Elmo 50mm pc lens which was very good. But that was with a Carousel screw thread and an Ektapro rack. Are 42.5mm threads used in cine projection?

 

[Petrochemist]

e differentI used to have an Elmo 50mm pc lens which was very good. But that was with a Carousel screw thread and an Ektapro rack. Are 42.5mm threads used in cine projection?

The cine projection lenses I've got are similar to my slide projection lenses just much smaller diameter (~1") but mine are probable all 8mm cine models. 16mm, 35mm & 70mm cine no doubt are different - to expensive for me.

 

[Ivo Stunga]

They are - image circle size and focal plane distance matters.