Experience with Mitutoyo 50x/0.75 HR?

[zed]

Hi All,

I'm curious if others have tried this objective - it has a lot of great features, especially the working distance-to-NA ratio. I've not found another objective that has >4mm working distance with an NA above 0.7 with Plan APO level corrections.

I'm currently using a 60x/0.7 ELWD BD M-Plan that works reasonably well - but for full frame it struggles at the corners and the CA is terrible. My CA corrections in post are starting to have detrimental effects on the image quality and I want to get away from this.

Some have suggested the Nikon 50x/0.7 L Plan - but the corrections are not to the same level as a Plan APO so I worry that the CA will still be troublesome compared to the M-Plan.

The Mitutoyo is god-awful expensive though - $5200USD is the best price I've found for it new.

My goal is to find the highest NA objective I can with a >4mm working distance.

Thoughts?

[Scarodactyl]

Reports from users on the forum are scant but positive iirc. The Chinese company that lothman recently found have a 50x/0.65 which, while not up to the 0.75 of the HR, does sound promising.

Incidentally I have the TU plan fluor 50x (not elwd, only 1mm) and correction is good but you do start to see some lateral CA at the corners on aps-c. That's the new and improved line so I wouldn't expect an L series to do better, though expectations aren't necessarily worth that much.

[Chris S.]

Zed,

I tested a specimen of the Mitutoyo 50x/0.75 HR for a forum member, comparing it with my Mitutoyo 50x/0.55 and Mitutoyo 100x/0.70. I’ve just now sent you a PM with a download link to the test images. They are PMax stacks on a Nikon D7100 APS-C body.

I found the 50x HR to be exquisite, and would like to own one, but really can’t justify the expense in my work. I felt fortunate that the fellow who owned the lens didn’t need it back right away, so I had the opportunity to use it for quite a while.

This said, while the working distance is large, so is the flat front of the lens. As I wrote in another thread:

Having tested a specimen of the Mitty 50/0.75 HR on a Nikon camera with an APS-C sensor, I can say that this particular optic does in fact cover this sensor.

However, the HR objective's 5.2mm working distance (short, compared with the 13mm WD of the 50/0.55 objective) is more limiting than I'd expected with a real-world subject. Given a fairly fat objective with a short WD, subject lighting is limited to sideways, glancing angles.

On a flat, printed test target, this was no issue. But when photographing a brown marmorated stink bug, pits in the bug's surface were left in the dark, the surface of the bug appeared very reflective, and the bug's surface topography was dramatically emphasized.

As technicians, lots of us at this forum can easily handle a 5.2mm WD. As photographers, we might not like the modeling this imposes for some subjects.

I'm currently using a 60x/0.7 ELWD BD M-Plan that works reasonably well - but for full frame it struggles at the corners and the CA is terrible. My CA corrections in post are starting to have detrimental effects on the image quality and I want to get away from this.

I have the non-BD version of this Nikon objective, which I think is the same optical design as yours. Have to agree with you on the CA. The Mitty HR is in a completely different world in terms of CA--essentially CA-free. In pixel-peeping, I think the 50x HR has a very tiny bit more false color than the two non-HR Mitties I tested it against. But we're splitting hairs, here--I don't think CA is objectionable in this objective.

--Chris S.

[Scarodactyl]

I'd definitely love a 50x HR, though I don't think my usage would do it justice. I'm usually using coax illumination at 50x anyway so the working distance would usually be wasted, though I wouldn't mind not having to crank the microscope down by 50mm to use my shorter parfocal objectives.

[zed]

Thank you Chris and Scarodactyl for your quick replies.

I was silently hoping that the differences would be minor - but the images Chris shared were quite impressive. I hope you are OK with me sharing, Chris - but I assembled a quick figure showing a cropped region from each example image at 100% (the 100x image was downsized 50% using PS' preserve details algorithm). Image is of a butterfly wing scale (not sure which species).



I am not sure I can (or want to) justify the cost of this objective either.....but it is quite compelling!

[Chris S.]

I hope you are OK with me sharing, Chris - but I assembled a quick figure showing a cropped region from each example image at 100% (the 100x image was downsized 50% using PS' preserve details algorithm). Image is of a butterfly wing scale (not sure which species).

More than OK--I'm delighted that you did it, and so well.

Species is, believe it or not, Urania ripheus--the sunset moth. Many of us know the shiny, curved scales, but this species also has areas with flat, very black scales like this one. I like it for tests such as this because it has details sized close to the resolution limits of these objectives.

I am not sure I can (or want to) justify the cost of this objective either.....but it is quite compelling!

I know exactly what you mean.

The fellow whose lens this is asked me to take delivery of it from the eBay vendor, and give it a test within the return window. Late at night, just after receiving this lens, I wrote its new owner something to the effect of, "Images to follow tomorrow, but there is no way you are returning this lens." He had gotten it for the price of a regular, non-HR 50x/0.55 objective on the used market--a feat that is extremely unlikely ever to happen again.

--Chris S.

[Scarodactyl]

The posted comparison is pretty dramatic!