What do you use to test your objectives?

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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smollerthings
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What do you use to test your objectives?

#1 Post by smollerthings » Thu Nov 18, 2021 3:29 pm

Diatoms? Where can I find some?
CD/DVD tracks?

Thanks :)

dtsh
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Re: What do you use to test your objectives?

#2 Post by dtsh » Thu Nov 18, 2021 4:12 pm

What you're checking should define what subject to use to an extent.

Diatoms are great for trying to get closer and closer to the theoretical limits of resolving power as many examples have pores and other structures that dip under the limits of visible light while having other structures which are above that limit, but they might not be as good for testing planarity of lower power objectives. In this regard not all diatoms are equal and some make better references than others as some have less noticeable features.
For planarity, I have been using a calibration slide. I has clear markings and should cover the field in all but extrememly low power objectives and in my case has been effective at making chromatic aberation apparent.
Probably one of my favorite subjects though are mosquitoes. Scales, especially on the wings, have a lot of detail and they're usually fairly flat. It's a bonus that just about all of us have them readily available for at least part of the year and one typically need do nothing more than wait for a subject to volunteer for microscopy.

Here is an early example of my effots to image a wing scale, this was with an AO 100x oil objective. I've learned a lot since then and should probably revisit it and see if I can do better.
210523_Aedes_scale_ao10_100x.jpg
210523_Aedes_scale_ao10_100x.jpg (62.62 KiB) Viewed 2006 times

BramHuntingNematodes
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Re: What do you use to test your objectives?

#3 Post by BramHuntingNematodes » Thu Nov 18, 2021 4:29 pm

dtsh wrote:
Thu Nov 18, 2021 4:12 pm
one typically need do nothing more than wait for a subject to volunteer for microscopy.
they are quite enthusiastic around here for sure

I have a stained pine wood slide that is essentially a set of high contrast parallel lines that works p. good also the lettering of a field finder slide I have reveals ca in even very good lenses
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

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patta
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Re: What do you use to test your objectives?

#4 Post by patta » Thu Nov 18, 2021 5:43 pm

Just used DVD and Bluray; great flatness and calibrated distance...but they're boring;
natural subject as above, much more interesting.

Alexander
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Re: What do you use to test your objectives?

#5 Post by Alexander » Thu Nov 18, 2021 7:36 pm

Calibration slides, as mentioned, are a great start to check focus resolution and contrast. After that the choice depends on your work. Do you epi-fluorescence or epi-darkfield or simple brightfield or phase-contrast or DIC? Just to mention a few. The proper sample depends on that.

smollerthings
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Re: What do you use to test your objectives?

#6 Post by smollerthings » Thu Nov 18, 2021 7:47 pm

I wanted to test 3 objectives I have, all 40x. Achro vs Fluor vs PlanAPO. I only do brightfield + darkfield + polarization.

I think I am gonna try insect wings and DVDs. Thanks for all your comments!

PeteM
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Re: What do you use to test your objectives?

#7 Post by PeteM » Thu Nov 18, 2021 10:44 pm

I start with micrometer-ruled calibration slides. Unlike natural specimens, they give a clear indication of field flatness and chromatic aberrations (often seen on the peripheral engraved lines) show up pretty clearly. Also let you easily determine field number.

Subjective comparisons of contrast might be better seen with a natural subject.

Cheap but usable Chinese micrometer marked slides are available on Ebay. Better quality ones, particularly those with black backgrounds and only the engravings transparent are useful to diagnose issues with flare and glare.

Scarodactyl
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Re: What do you use to test your objectives?

#8 Post by Scarodactyl » Fri Nov 19, 2021 9:32 pm

I use a wafer for my epi objectives, in comparison to my known good (or known gpod enough anyway) examples. Not much use for transmitted light though.

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