Adapting a lens that has no focus?

[Yan Lauzon]

I never heard of process lens.

The fact I can find focus very near the camera makes me doubt my initial suspicion that it may have been an incomplete lens, and the iris tells me it may not be a projector lens.

As you said the enlarger lens are generally m39, so I am still in the dark.

I tried to add basic elements after the lens (magnifying glass) to see how it would behave but all I get is bigger unfocused images.

No matter what it was, it is instructive and a fun project.

Thanks for chiming in!
Do you have pictures or other details on those process lens? What was their use?

 

[petrochemist]

The reprographic was basically a vertical large format camera for copying artwork, in the days before desktop publishing. The original was placed under a glass sheet at the bottom, the image size & focus adjusted by two cranks (one raising the subject the other moving the lens) with both scales the same the image should be focused but this could be checked on the top glass screen, before turning off the lights, adding the film, turning on the vacuum pumps then making the exposure. Processing was by adding a second (different) film sheet & feeding through a roller driven bath - then peel the two halves apart after about a minute. No need for stop baths etc. Results where very high contrast - pure Black & White needing variations in the process if half tones were needed. The processing system as a whole was called Photo-Mechanical Transfer.
Aperture was not normally altered but I believe the artwork could be tilted for more advanced use which could need aperture changes - I only ever did flat subjects, when working as my Dads gophur in school holidays.

Similar lenses can I gather be found in some photocopiers, and other such devices.

I've heard these lenses are high quality, but I lost track of my dad's one over 35years ago & have never managed to spot one on E-bay...

 

[Yan Lauzon]

Thanks a lot for the explanation. That must have been an interesting process

 

[Yan Lauzon]

I just received two 12-17mm hélicoïds. Just one and I can use it portrait style with my m42 "corrected" adapter, two and I can close up much more.

The corrected adapter intends to bring m42 to focus at infinity on my camera, and includes a corrective lens. I ordered a non-corrective one that just has not arrived yet.

With this correction, by comparing on another lens, I can safely say it makes a 80mm with wider than f/4.5. My gross calculation would put it at f/4

Ill see what it gives without lens correction.

 

[Yan Lauzon]

I brang the lens (and camera) to the dojo today for some testing, and while it works like a charm (and is very crisp) at close range, it is just shy of being sharp at anything not super close. I guess with the corrective lens included in that adapter, the 12mm is just a bit too much.

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

 

[petrochemist]

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

Surely your free-lensing tests confirm it will work. with the lens 1-2cm from the camera. You might need to get the lens a little closer than your assembly with the corrective lens to ensure infinity focus. It should be slightly wider without the corrective lens - I've heard the corrective lens works a little like a 1.1x or 1.2x teleconverter.

 

[Yan Lauzon]

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

Surely your free-lensing tests confirm it will work. with the lens 1-2cm from the camera. You might need to get the lens a little closer than your assembly with the corrective lens to ensure infinity focus. It should be slightly wider without the corrective lens - I've heard the corrective lens works a little like a 1.1x or 1.2x teleconverter.

That is what I believe also.
With the correction, my gross calculations placed the lens from 60mm to 72mm, so a 1:1.2 ratio.

Let's just hope it focuses right when I assemble the thing with a standard adapter. I can't find any hélicoïds thinner than 12mm.

 

[petrochemist]

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

Surely your free-lensing tests confirm it will work. with the lens 1-2cm from the camera. You might need to get the lens a little closer than your assembly with the corrective lens to ensure infinity focus. It should be slightly wider without the corrective lens - I've heard the corrective lens works a little like a 1.1x or 1.2x teleconverter.

That is what I believe also.
With the correction, my gross calculations placed the lens from 60mm to 72mm, so a 1:1.2 ratio.

Let's just hope it focuses right when I assemble the thing with a standard adapter. I can't find any hélicoïds thinner than 12mm.

One of my adapted lenses actually pokes out of the rear of the helicoid when at minimum most of it sits inside the helicoid. I did have to get a wider helicoid to do that. The lens in question has no aperture control eitherso a recessed mounting doesn't get in the way

 

[Yan Lauzon]

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

Surely your free-lensing tests confirm it will work. with the lens 1-2cm from the camera. You might need to get the lens a little closer than your assembly with the corrective lens to ensure infinity focus. It should be slightly wider without the corrective lens - I've heard the corrective lens works a little like a 1.1x or 1.2x teleconverter.

I finally received my m42 adapter - it's as thin as can be, not even 1mm of metal. The bayonet is literally around the m42 threads.

Yet at about 3-4 meter I am just a bit shy of achieving perfect focus. It works great closer.
I think I need a thinner helicoid than 12mm.... Does that exist?

 

[petrochemist]

I wonder if it's going to work correctly sans corrective lens. What was I thinking when I got that adapter w/ lens anyway...

Surely your free-lensing tests confirm it will work. with the lens 1-2cm from the camera. You might need to get the lens a little closer than your assembly with the corrective lens to ensure infinity focus. It should be slightly wider without the corrective lens - I've heard the corrective lens works a little like a 1.1x or 1.2x teleconverter.

I finally received my m42 adapter - it's as thin as can be, not even 1mm of metal. The bayonet is literally around the m42 threads.

Yet at about 3-4 meter I am just a bit shy of achieving perfect focus. It works great closer.
I think I need a thinner helicoid than 12mm.... Does that exist?

I don't think I've ever seen one!

Can you recessed your lens deeper into the helicoid? There are M42-M52 helicoids and even some at M65 IIRC.

My 50/1.2 projector lens is mounted so the rear of the lens would have stuck out the back of the helicoid & adapter - there was some spare metal behind the last element that I've trimmed off so it's now roughly flush with the back at the helicoids shortest.

 

[Yan Lauzon]

Recessing it inside the helicoid isn't something I considered yet. How do you attach it inside?
The lens is thin and may fit within something not too wide. Maybe I can adapt the body to screw in the adapter directly?

On another note, I found out a supposedly 10-13.5mm helicoid made by a company named pixco, but nowhere I see them available in Canada. I wonder if it's a US venders with a bad inch-cm conversion...

 

[petrochemist]

Recessing it inside the helicoid isn't something I considered yet. How do you attach it inside?
The lens is thin and may fit within something not too wide. Maybe I can adapt the body to screw in the adapter directly?

On another note, I found out a supposedly 10-13.5mm helicoid made by a company named pixco, but nowhere I see them available in Canada. I wonder if it's a US venders with a bad inch-cm conversion...

It's the middle one of these three, with a stepping ring glued (hot melt) to the barrel about an inch back, where there happened to be a convenient ridge.
3 projectors small by Mike Kanssen, on Flickr

The other two both fit the same helicoid (a 35-90mm long M42-M52 model) via similar means.

 

[Yan Lauzon]

Recessing it inside the helicoid isn't something I considered yet. How do you attach it inside?
The lens is thin and may fit within something not too wide. Maybe I can adapt the body to screw in the adapter directly?

On another note, I found out a supposedly 10-13.5mm helicoid made by a company named pixco, but nowhere I see them available in Canada. I wonder if it's a US venders with a bad inch-cm conversion...

It's the middle one of these three, with a stepping ring glued (hot melt) to the barrel about an inch back, where there happened to be a convenient ridge.
3 projectors small by Mike Kanssen, on Flickr

The other two both fit the same helicoid (a 35-90mm long M42-M52 model) via similar means.

I'll take some measurements and shop yet again for parts...

Sticking a stepping ring isn't a bad option if it fits. Thanks for the idea.

 

[petrochemist]

Sticking a stepping ring isn't a bad option if it fits. Thanks for the idea.

I like to keep a good stock of different sizes available for things like this (as well as for filters). There are an amazing variety of them available, many at nice low prices, if you can wait a few weeks. If required a little tape underneath or a little gentle sanding can sometimes adjust the fit of one that's not ideal. Nothing complicated needed, its the adapters that go behind the lens that get tricky to jury rig.

 

[Yan Lauzon]

Trying things with my lens today... The way it is built wont adapt well to a m52. The whole thing is a bit less than 60mm diameter. If I stick it to a m65, it will have to be on the aperture ring, so I'd ave to turn the whole lens from the tip for aperture. I still don't know how I'd make it hold in place.

I tried to open the lens in case I could change some properties, but it's been tampered with in the past and one screw is broken in place, so that won't happen

I got into thinking... 10mm isn't huge. I almost get there with just unscrewing the m42 adapter.

Maybe all I need is a m42 macro extension ring