Is Leica 1x plan achro 0.25 vignette expected

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

NickM
Posts: 30
Joined: Thu Mar 07, 2013 8:35 pm
Location: Dallas, TX

Is Leica 1x plan achro 0.25 vignette expected

Post by NickM »

Hi. I've finally completed the Leica set of 1, 1.5, 2, 3 and 4. The 1X has vignetting regardless of the iris setting on the objective.

Is this expected for a 1x? None of the others do this.

Scarodactyl
Posts: 685
Joined: Sat Apr 14, 2018 10:26 am

Re: Is Leica 1x plan achro 0.25 vignette expected

Post by Scarodactyl »

I assume these are the macro objectives off the forensic comparators?
Not sure what their rated field number is. On what setup are you seeing vignetting?

NickM
Posts: 30
Joined: Thu Mar 07, 2013 8:35 pm
Location: Dallas, TX

Re: Is Leica 1x plan achro 0.25 vignette expected

Post by NickM »

Hi and thanks! The setup uses a Nikon MDC lens (adapter for camera lens) on a c-mount. Above is Canon 50mm 1.4 and M6 II. Only the 1x vignettes a bit.

I think this rig was designed for gemstones. Its been >10 years since I bought the first parts.

Image

Scarodactyl
Posts: 685
Joined: Sat Apr 14, 2018 10:26 am

Re: Is Leica 1x plan achro 0.25 vignette expected

Post by Scarodactyl »

Ohhhh right I remember this one now. Basically one half of a forensic comparator done up for macro work. I think you're probably going to be SOL on getting much direct support on it since this is not a widely used series of scopes or objectives and it looks to be a custom job on top of that.
From what I can see it looks to be afocal? Sometimes using a normal camera lens for afocal can cause vignetting because of entrance pupil location so flat pancake lenses are preferred. Some closeups so we can see and identify each element would help. But if that's one of thr Nikon adapters meant for a point and shoot that might be your problem too.
There seems to be a ton of space between the objectives and the eyepiece. I am not sure if this setup is finite or infinity corrected, and if there are corrective eyepieces involved.
Good grief is that an AO stereostar focus mount holding the stage?

NickM
Posts: 30
Joined: Thu Mar 07, 2013 8:35 pm
Location: Dallas, TX

Re: Is Leica 1x plan achro 0.25 vignette expected

Post by NickM »

Working backwards, the elevator holding the nose piece and tube is labelled Leica. The heavy stage is McBain. Yes afocal with infinity corrected plan achros.

The objectives are designed for a large working distance, which is the primary benefit from my perspective.

The Nikon MDC is not causing a problem. It works very well.

I worked out the entrance pupil by matching the lens to the setup. Lugged the rig to a lens rental outfit and found the ideal lens (50mm 1.4) that way.

The key point is that 4 of the 5 objectives have no vignette. Thinking out loud, the numerical apertures are progressively larger at lower mag. So at 0.10, the 1x has the longest working distance (being the shortest objective physically) and so the smallest cone striking the sensor. So it makes sense that it doesn't quite fill the sensor in this setup. The image is still usable and easily cropped in post, retaining a larger field than the 1.5.

Well at least there isn't anything wrong with the 1x. Thank you for your thoughts and inspiration :)

ray_parkhurst
Posts: 2854
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Is Leica 1x plan achro 0.25 vignette expected

Post by ray_parkhurst »

The Leica system you've pictured is their "video microscope". I've owned a few of them over the years, and indeed still have one in a box somewhere. The optical system is desiged for C-mount applications, so coverage is limited. The higher mag objectives do cover more than C-mount, but the 1x and 0.66x vignette on APS-C.

I believe the tube lens is ~100mm, so you might be able to replace it with a longer FL and get better coverage.

edited to add: it may also be the tube lens is the only issue with vignetting, but since the higher mag objectives don't vignette, it's more likely due to the 1x objective coverage.

Post Reply Previous topicNext topic