Flange Focal Distance Part II

So apparently my theory on Flange Focal Distance being a factor in my focusing problems seemed to be a dud. It turns out that I can hold the camera actually a fair distance away from the flange mount without any observable degradation in image quality.
In hindsight this makes some kind of sense. As the microscope acts as the camera’s lens, the light hitting the sensor must be relatively parallel.

To test this I actually decoupled the camera from it’s mount and shot lens-less from a ways back in a darkened room.

So going from fully attached to several dozen millimeters out changed my image impressively little.


Microscope Focal Distance 2


Microscope Focal Distance 1

Hand Held










Microscope Focal Distance 4

Hand Held

Microscope Focal Distance 3





Flange Focal Distance

I am not a professor of optics.

That being said I do understand that there’s a lot to learn about hooking a camera up to a microscope and I am woefully ignorant of the┬áminutia.

But this is science and it is full of venturing into the unknown, even if many have already figured it out.

So one of the problems I have been having with the Versamet microscope is that everything on the camera was out of focus compared to the eyepiece. I did a little correction with the fine adjustment focus knob to get around the issue. But being limited to a Canon 5D without live view meant I had to focus everything through the eyepiece. Cumbersome and uncomfortable are appropriate words here. This meant that the photo quality suffered.

Then I discovered Flange Focal Distance. It was something I was vaguely aware of but didn’t know it was critical. When light exits the rear of a lens heading for the image sensor (or film), the light rays aren’t actually parallel. Thus placing the sensor closer to or further away from the lens flange than designed can lead to a fuzzy shot.

From Wikipedia

From Wikipedia

Now it seems that the Leica M mount that originally came with the microscope had a focal distance of 27.8 mm while the Canon EF mount tops in at 44.0 mm. There’s enough of a disparity there to make me think that this may be a factor in my images.

Solving this issue should bring my eyepiece focus and camera focus to the same point. Hopefully it will also help my falloff problem and light up the edges of my pictures. Unfortunately with my microscope out on loan I can’t do anything about this at the moment. I’ll provide an update when I get a chance to tackle this problem.

A Lens Adapter for a Versamet 2 Surface Microscope

One of the reasons that I bought my Canon 5D was to be able to share some of the interesting things I’ve seen through my Versamet 2 Surface Microscope.

The problem is that Unitron only made adapters for Lecia cameras. My EOS camera takes the EF series of lenses. Unfortunately I can’t seem to find any engineering drawings of the lens mount online.

My solution is to make my own from scratch. A little turning here, a little CNC code there and I should have it.

Here is the Solidworks rendering of the lens adapter. There are a few things I found difficult to measure, but I should be able to make do.

lens adapter

When I’m done with this, I’ll have the engineering drawings available so the next guy (or girl) will be able to skip this step.

Hooray for Machine Shops.