Raynox DCR-150 tube assembly with flocking

[rjlittlefield]

The 10mm segment has no flocking and the same diameter as the other tubes. I remember having tried the FF camera before (with the 10mm segment included) and there was no vignetting.

I expect the other tubes are flocked, and I can see a rough edge on the vignette consistent with flocking.

It is the absence of flocking on the 10mm tube, leaving a larger clear diameter, that makes the vignette go away. The extra extension does give some more magnification, but if the extension were flocked also, giving a smaller clear diameter, the vignette would still be there.

If I had this problem and I wanted to work at large NA where the extra extension could be problematic, then I would remove a 10 mm strip of flocking around the end of the 50mm tube, and omit the extra extension.

--Rik

[Ultima_Gaina]

The 10mm segment has no flocking and the same diameter as the other tubes. I remember having tried the FF camera before (with the 10mm segment included) and there was no vignetting.

I expect the other tubes are flocked, and I can see a rough edge on the vignette consistent with flocking.

It is the absence of flocking on the 10mm tube, leaving a larger clear diameter, that makes the vignette go away. The extra extension does give some more magnification, but if the extension were flocked also, giving a smaller clear diameter, the vignette would still be there.

If I had this problem and I wanted to work at large NA where the extra extension could be problematic, then I would remove a 10 mm strip of flocking around the end of the 50mm tube, and omit the extra extension.

--Rik

I shaved off 5mm and the vignetting is gone (with 3mm it was still there)!

Rik, hats off! This is perfect now!

You are the best!

[rjlittlefield]

Excellent -- I'm very happy to hear that it's working well for you now.

One thing to keep in mind for future use: some vignette may return if you move the objective farther away from the tube lens, or if you use an objective that provides an effective aperture that is much wider than the f/22 that you're using now.

The reasons are different in those two cases. If the objective is moved farther away from the tube lens, then the exit pupil of the combo moves farther out also. This causes the light cones that construct the corners of the image to become more parallel with the optical axis, so the shadows of the flocking will move inward and may reach the corners of the frame. If you use a wider aperture, then the outermost rays of each cone for the corners of the image will be more parallel to the optical axis, so those rays may get blocked.

A reasonable approach in both cases would be to shave off some more mm of thick flocking. But I wouldn't do that until I saw a problem.

--Rik

[santiago]

Great posts on this topic lately, a lot of good info

[lothman]

Hello,

a question to the community. As far as I read here in forums reversing the Raynox DCR-150 improves things and also adding some distance between microscope lens and tube lens improves results.

So for those of us who would like to use a reversed Raynox DCR-150 as tube lens and Mitutoyo microscope lens, a modified Rafcamera-Adapter would be handy.

this version
https://rafcamera.com/adapter-m26-to-m42x1-cone


could be had with M43x0,75 female thread instead of the M42x1 male thread, so the reversed Raynox DCR-150 could be screw into directly.

I asked rafcamera and if we get 5 interested people, they would make the adapter to similar costs ( estimated around 30$ +-).

I would need two of them, so who else is interested?

regards
Lothar