GP slide of Blastobasis sp

JKT · Post by **JKT** » Wed Feb 26, 2020 2:37 pm

First image with Nikon Plan APO 20X / 0.75 DIC N2/ 0.17 WD 1.0:

3000x2000

Other equipment:
- Canon EOS RP (FF)
- Raynox DCR 150
- Stackshot (55 images with 1 um step)
- 3x Yongnuo YN560-III & DIY flash diffusor

The image shows full frame and the "span" is about 1.33 mm.

The hook at top right corner seems to be unsharp. Could be I'm exceeding the image circle in the objective or Raynox. I don't think it was outside the stack depth.

The resolution requirement of RP shouldn't even scratch the capabilities of the objective, but this is what I got it for and it seems to do the job ... even though the step size should be about half.

rjlittlefield · Post by **rjlittlefield** » Wed Feb 26, 2020 3:26 pm

Looking at the high res image, I agree that everything in the upper right corner looks soft, compared to what I see other places in the image.

It doesn't look like you've missed including it in the stack -- that would look way worse!

Noting 55 images with 1 um step, I'm wondering if that corner happens to be deep in mountant and we're seeing spherical aberration. Figure 3 at https://www.microscopyu.com/microscopy- ... correction suggests around 70% loss of contrast for fine detail with an extra 0.055 mm of cover glass thickness at NA 0.75.

I don't know anything about the image circle of that objective.

Image circle of the Raynox DCR-150 easily covers full-frame.

I see also a bit of vignetting (dark corners) that could be due to the objective. It's quite gradual, doesn't look like shadowing from extension tubes with a small bore.

One quick question... I assume this the slide is male genitalia of a small moth. But what exactly does "GP" mean?

--Rik

JKT · Post by **JKT** » Wed Feb 26, 2020 4:14 pm

If I recall correctly, the right corner was rather high in the stack, so there shouldn't be any more mountant there. And the transition from sharp to non-sharp is rather fast, which it shouldn't be if there was same amount everywhere. Likely requires further testing.

There is also a baffle to prevent reflections inside the tube. It shouldn't be on light path, but...

Another check required.
Edit: On second thought - it shouldn't be on light path for FINITE objective. Infinite with tube lens is a different story.

It is indeed male genitalia of a small moth. Wingspan maybe 12 mm or so. Now that you asked I'm not quite sure where the GP comes from. It could be Genital Preparat or some such. Could be German origin?