A glut of Mitutoyo 7.5x Plan Apo Objectives ?

[Macrero]

I have one of those, the DIC N2 20/0.75, WD 1.0mm. Haven't tested it yet though. Will test it and will report back how it does, though I doubt that result will be optimal without coverslip.

- Macrero

[Pau]

I have one of those, the DIC N2 20/0.75, WD 1.0mm. Haven't tested it yet though. Will test it and will report back how it does, though I doubt that result will be optimal without coverslip.

Not much need to test it, without cover it will perform very poorly for sure. Likely you will get an image but blurred because the massive spherical aberration, up to 0.30 - even 0.40 it will work, not at 0.65 and even less at 0.75.

[Macrero]

Not much need to test it, without cover it will perform very poorly for sure. Likely you will get an image but blurred because the massive spherical aberration, up to 0.30 - even 0.40 it will work, not at 0.65 and even less at 0.75.

Yeah, I know that performance will be far from optimal, but wanted to see how bad the coverslip correction affects IQ at NA 0.75. Just did a quick test-stack at 21X.

100% crop:

https://images2.imgbox.com/b6/6d/TwSbGtZC_o.jpg

Virtually 0 CA, but "fuzziness" is obvious.

- Macrero

[Lou Jost]

That's a remarkably clean image, almost no CA.

[Macrero]

That's a remarkably clean image, almost no CA.

Lou,

yes, I was just editing my previous post to add the lack of CA. I would say objective could be "usable" without a cover, but not sure it is worth bothering with working at 1mm WD and with ridiculously short steps, to end up getting a far from optimal result... Will make another test with a 3D subject though, just for fun...

- Macrero

[Lou Jost]

Which model was this? VC?

[Macrero]

Nope, this one:

https://images2.imgbox.com/66/1f/tp1uStLF_o.jpg

[Lou Jost]

Good, that's the same one referred to above, which I just bought a few days ago and which is currently flooding the market.

[Macrero]

A quick "3D" test stack with the Raynox 250 at 12.5X.

https://images2.imgbox.com/c0/8f/mPYL4XBZ_o.jpg

100% crop of a single frame:

https://images2.imgbox.com/3a/30/oebND6IZ_o.jpg

The lack of CA is striking. Coverage at 12.5X is surprisingly good too for an OFN 25 objective.

[Lou Jost]

So that's still no coverslip, right? Nice, no vignetting or CA

[ChrisR]

Looks good to me, there's some nice fine detail.
Decent lighting too, for 1mm!

[Macrero]

No, no coverslip there. Wanted to try it with coverslip with scales or some flat subject, but can't find the box with coverslips I'll keep looking tomorrow. Objective should work brilliantly as intended.

Lighting is tough with 1mm WD, I could have done better (not much better though...), but that was just a quick test.

- Macrero

[Lou Jost]

By the way how did you light that?

[Macrero]

3 LED lamps (800lm each) and a simple plastic difuser. Some reflector would have helped with shadows/dark areas, but I did not bother with that for the test.

[Pau]

Not much need to test it, without cover it will perform very poorly for sure. Likely you will get an image but blurred because the massive spherical aberration, up to 0.30 - even 0.40 it will work, not at 0.65 and even less at 0.75.

Yeah, I know that performance will be far from optimal, but wanted to see how bad the coverslip correction affects IQ at NA 0.75. Just did a quick test-stack at 21X.

100% crop:

https://images2.imgbox.com/b6/6d/TwSbGtZC_o.jpg

Virtually 0 CA, but "fuzziness" is obvious.

- Macrero

Your result is not so bad for a 100% crop and correction mismatch.
An interesting test would be to shot the same subject with the same illumination with a good no cover 20/0.40 like the Mitutoyo 20/0.42 and compare the images at the same subject magnification to see if the actual resolution is similar and the Nikon is only losing its theoretical advantage due to its high NA or more due to spherical aberration.

I can't perform this comparison but when I receive my copy I will be able to compare it with no cover Nikons 40/0.65 and 40/0.80 although I think that I already know the result