Does anybody know how to build the setup for the Mitutoyo M Plan Apo 50x / 0.55 in the best way?
I have been taking photographs using mitties: 2x, 5x, 10x and 20x without any problem.
But the 50x doesn’t like my construction
I have already tried to change the length of the TL and to close the iris.
What is the problem of this lens?
If your olympus 50x works fine, and your other Mitutoyo objectives play well with your tube lens, then it seems to me like the simplest explanation would be that your Mitty 50x is a lemon?
Photos will help. If your setup is adequate, vibration control wise for 20x, I can't it being a problem for the 50x with an NA merely 0.13 above the 20x.
Sorry to say, but maybe your 50x is a dud. These second hand metallurgical objectives are usually salvaged from industrial setups that see heavy abuse from its users and the environments. Conversely, salvaged life science objectives usually originate from places of relative care and expertise, such as labs. A cosmetically flawless objective isn't always indicative to its optical cohesion.
Anyhow, a photo to exemplify your issues will help.
Few questions:
What's the observed issue? 0.55 is close enough to 0.42 to work fine in the same rig (and it never will be equally sharp at the sensor side)
what's the NA of your Oly?
Are both 50X meant for non glass covered subjects?
Are you able to return the Mitutoyo?
Therefore I would say that I have to optimize my setup with DCR-150.
So, Mitu 50x is probably a little bit picky and expects a perfect configured setup.
BTW, Oly UMPlanFI 50x / 0.80 works without any problem with the DCR-150
Hi Pau,
Yes, originally the Raynox had been focused to infinity but I have already changed that while I was looking for the improvement :-)
But I have noticed that the small closing of the iris improves the quality of the image.
Best,
ADi
Usually, closing the iris will improve images somewhat because it acts like a baffle. I think it cuts out stray light reaching the objective. That's why I sometimes plant an iris at the exit pupil of the tube lens, it does bring slightly higher contrast when closed down correctly. However, the Mitutoyo itself is effectively closing the iris already. Your NA 0.8 objective is expected to be pickier than any 50x Mitutoyo (highest resolution is 0.7, their 50x HR version).
Where's the Raynox? I can't exactly figure it out its placement from the photo. As others have suggested, focusing it to infinity could be a good starting point. Additionally, try mounting the objective as close to the Raynox as possible.
Like others, while reading this thread, my first thought was that perhaps you have a bad specimen of the Mitutoyo 50x/0.55. But your observations that this objective behaves better on your Canon prime lens than on your homemade Raynox-centered converging lens assembly, and that it also behaves better on your home-made lens assembly when stopping down the iris, give me pause. To me, this suggests the possibility of light bouncing around somewhere in your homemade lens assembly--in other words, the possibility of uncontrolled internal flare.
If this is the problem, it would likely appear as reduced contrast/presence of veiling glare. Here is a case where, if you posted images taken through your Mitutoyo 50x on your homemade assembly, and images taken through your Canon lens, we might get a sense of what problems are occurring.
Any chance you could post such images? Also, any chance you could double-check your Raynox assembly to make sure there is no surface, no matter how small, left unflocked?
I regularly shoot with "all" the mainstream Mitutoyo objectives on the same tube lens assembly: The Mitutoyo 2x/0.055, 5x/0.14, 7.5x/0.21, 10x/0.28, 20x/0.42, 50x/0.55, and 100x/0.70. Also, I've tested and used an HR 50x/0.75 objective. In no case have I had to change anything about my tube lens assembly to accommodate any of these objectives. I don't use a Raynox DC 150 diopter as a converging lens, but rather, a Mitutoyo MT-1 official tube lens; this said, I don't believe that this distinction makes any difference in your case.
So I'm back to wondering about internal flare. If flare exists anywhere, in any form, in your converging lens assembly, you can have problems; and such problems may be far more visible with one objective than others.
F = Flocked light trap from Protostar
i = Iris M42 (a little bit closed)
BTW, the distance between the lens an the Raynox = 50mm
I have already used a constant iris on the camera-side
with the diameter = diagonal of the chip
but I haven’t seen any improvement and I have removed it.
Maybe I should put this iris again especially for the Mitu 50x.
Are you sure your dimensions are right? It seems that you are using Raynox reversed. I'm not, but the distance from sensor to the rear flange of Raynox was something like 210mm. In your picture the rear flange is roughly 230 mm from the back of the rear cap. The sensor is likely a bit further still. Raynox is known to work on short focus, but extra extension is something else. I doubt there is that much difference in pupil locations.
Using the Mitty with 100mm objective should give you ~double the resolution compared to Raynox, so it is no wonder that looked better. The 70-200 is another matter, if you tried it at 200mm.
