Optem HR 20x

[Scarodactyl]

Here's a quick test of the Optem HR 20x. These objectives are well known for their small image circle and bad curvature of field, though I've only seen test pics from the 10x (I actually had a 10x for a bit too, and the results were bad on aps-c but not quite as dire as that). But I found a 20x really cheap on eBay and had the thought that, since I have a magnification changer on my microscope, I could easily push it up to 40x and maybe that would crop the troublesome corners. Then I would have a 40x/0.60 with the same working distance as a Mitutoyo 50x and slightly higher resolution at a much lower price point. I do have a couple of better high mag objectives, but my Olympus lmplanfl 50x/0.80, while great, is a big pain to use with my other objectives because of its 45mm parfocal length (lots of cranking the whole assembly down and hoping I don't accidentally hit one of my protruding mitutoyos with something) and epi DIC results are also not exactly inspiring. My 40x/1.0 water immersion objective totally rules but isn't suitable for every sample, and especially not for looking at surface textures. So there is a case to be made for this objective, but what is image quality actually like?
So I did a quick shootout between it and my Mitutoyo 20x.
At 20x the results are just what you'd expect:



The HR is obviously brighter and has a nice, higher resolution image in the center but has terrible edges and corners. Nothing as bad as that 10x HR test but reasonably unusable at 20x nevertheless.
Now for the interesting comparison. For the 40x shots I brightened the mitutoyo 20x crops to make comparisons easier.



The HR objective has the clear edge in the center and the corner. Both of these crops are from single photos so at 40x planarity is really no longer a problem. There is some CA visible on both, a bit more green on the HR but nothing too insane. Here are some 40x shots in that first area which are better for CA, though focus on the mitutoyo was probably not quite perfect:


I didn't grab the pictures but epi DIC performance is identical between the mitutoyo 20x and the optem 20x on my setup.
Overall, if a long working distance or parfocality with other 95mm parfocal objectives is important then this objective might have a place--basically, if you have a use for a Mitutoyo 50x/0.55 then this would probably be a suitable substitute as long as you can push the magnification up. I think I'll probably keep it in my lineup, particularly for epi DIC where minor CA seems to be unimportant.

[RobertOToole]

Interesting examples!

Should add the note that the Optem HR objectives are private label for Edmund Optics as OE HR objectives but it looks like they just sell the Optem branded units now but the OE units are still out there for sale. Optem also makes Kramer Scientific HR Objectives, 5x, 10x and 20x, these have black and yellow barrels.

Do you know who makes Navitar HR Plan APO Objectives? They make a 6x 0.3 but the FN is only 22.

https://navitar.com/products/imaging-op ... bjectives/

[Scarodactyl]

Thr EO situation is a bit odd, since they still have it labelled as EO HR on the site but the picture is of an optem objective.
My 10x was a Kramer-labelled one. I do like the snazzy blaxk and gold look.

2022 edit: I got an Optem-labelled 10x and it perfoems like the one linked above. Unusable on a microscope unlike the 20x which was a lot more usable even if the edges were still poor.


I think Navitar actually makes their own optics (at least some), a real novelty in today's world if so. They also offer custom objectives made to spec which sound like fun.
My mag changer also does 1.25x, perfect for turning a 22mm fn to 27.5 for aps-c, so I'm ready if I ever find one.

[RobertOToole]

Thr EO situation is a bit odd, since they still have it labelled as EO HR on the site but the picture is of an optem objective.

Makes me wonder why they don't just discontinue the private labeled units. Noticed they have some well spec'd 16K line scan lenses, Techspec LS, to complete with Xenon-Sapphire: f/2.9-3.2, 82mm IC, 2.5-3x. $4K! I wonder where these are made? https://www.edmundoptics.com/f/ls-serie ... ses/39596/

My 10x was a Kramer-labelled one. I do like the snazzy blaxk and gold look.

Kramer-labelled HRs occasionally appear at really low prices.

I think Navitar actually makes their own optics (at least some), a real novelty in today's world if so. They also offer custom objectives made to spec which sound like fun.
My mag changer also does 1.25x, perfect for turning a 22mm fn to 27.5 for aps-c, so I'm ready if I ever find one.

Yes, true, I think those are the Pro-Raptar line. An optical designer that used to post on DPreview discussed one of the Pro-Raptar designs he worked on for Navitar.

Best,

Robert