Acheiving parfocal direct projection (APS-C) on the Wild M420

Here you can discuss DIY adaptations to the microscope.
Post Reply
Posts: 835
Joined: Sat Mar 03, 2018 9:09 pm

Acheiving parfocal direct projection (APS-C) on the Wild M420

#1 Post by Scarodactyl » Sat Oct 20, 2018 11:11 pm

Note that you can also buy a premade version of this on eBay from seller mmalkin15, which is where I got the idea from: ... 2811185124

This is a mini-project I recently completed and I figured I should share the steps here. I didn't take enough pictures as I was going but I think there's enough information here to make it work.

The Wild/Leica M420 is an exceptional piece of equipment, with many of the benefits of a stereo microscope but with much better photographic capabilities. They are especially popular for gem photography but could be used for almost anything that needs medium to low mag and long working distances.

As it comes, the Wild M420 is like many microscopes:suoer easy to adapt a c mount camera (there is a 38mm tube that accept adapters), but harder to adapt a dslr. You'd need a tall stack of optics above the tube to pull thr image up and get it appropriately sized for a dslr, and appropriate mounting hardware is sort of scarce.

Direct projection onto aps-c is am agtractive option. The image circle is plenty big, but the provided tube is a little too tall for the camera to be parfocal with the eyepieces.

Yeah, you could take a hacksaw to that Wild tube, but you won't.

So now for the obvious solution, which is to remove and replace the camera tube entirely. Fortunately the tube is held onto the top plate of the microscope with just three screws. The top plate of the m420 is very easy to remove, with four flathead screws holding it on. Inside you'll see a lens (I'd note this lens was filthy when I got my m420, but thankfully was very easy to clean). The tube is connected to the top plate of the M420 with three 2.5mm hex screws. You'll need to remove the entire plate and reach down through the top of the tube with a long hex wrench to unscrew them. Once you get the tube detached from the top plate, you'll see the bottom of the tube looks like this:
It sits down in a little round recess in the top plate of the M420. So to make an adapter here you'll need something round with the right diameter to sit down in the recess, a bit of meat to drill holes in for the screws, and optionally that also fits into the central hole to keep centering. The answer to this is a simple female M42 to male C-mount adapter:
I used this one (actually a T-2 to c-mount adapter), which is very thick and well-made, perfect for this task. Pictured here after I marked it with the approximate location of the screw holes. You'll need to drill holes in it big enough for the screws to fit through, but small enough for their washers not to fall in. Marking the locations exactly is difficult, but fortunately you can get it a little bit wrong.
I screwed up a bit but it doesn't matter at all, just moved one hole a bit.
The other thing you have to do is file down the c-mount threads a bit, since the hole is a bit less than an inch in diameter. I used a grinder for most of it and coarse sandpaper for the corners.
This adapter is rough but nobody will see the ugly parts. And even though I bought two adapters to give me some room to mess up it worked perfectly on my first try.
From here it's just a matter of adding a t2-to-m42, a male-male M42 adapter and spacers of the appropriate length to get the camera parfocal. A cheap chinese helicoid is good for getting perfect parfocality. They have some wiggle if any force is put on them, but that isn't an issue with remote shooting.

Posts: 144
Joined: Mon Jan 21, 2019 4:54 pm

Re: Acheiving parfocal direct projection (APS-C) on the Wild M420

#2 Post by geo_man » Tue Jun 23, 2020 11:10 pm

I recently purchased a Wild M420 and Scarodactyl informed me that it was even easier to attach my Canon M50 mirrorless APS-C camera to the existing photo tube than that described here for a DSLR. That because the sensor is closer to the front of the camera.

All I needed were the following. Both inexpensive. The threads between the two adapters don't mesh perfectly but they work fine.

38 mm to T2 Microscope phototube camera adapter ... 2749.l2649
Slim 1mm M42 Lens to CANON EF-M Mirrorles Camera adapter ... 2749.l2649

The camera is perfectly parafocal with the eyepieces throughout the zoom range. The FOV in the camera is a bit bigger than through the eyepieces; a nice surprise.

Thank you Scarodactyl for walking me through the solution.

Here is my first model; a carpenter bee.
2020-06-13 14-36-44 (C,Smoothing4).jpeg
2020-06-13 14-36-44 (C,Smoothing4).jpeg (229.25 KiB) Viewed 186 times

Post Reply