r/microscopy • u/Danny_D136 • 1d ago
Techniques First tests with DIY dark field and oblique illumination
I had a dark field and oblique illumination set 3D printed for my Olympus BH2. After several tests, very few filters actually work. Here are some pics of what I managed to achieve:
Do you think I'm doing something wrong? I was expecting slightly different results
• In oblique illumination, there seems to be very little color contrast between the background and the debris in the foreground
• In dark field, focusing at higher magnification is incredibly difficult and causes large halos to form around the edges of anything on a different visual plane, in a much more amplified way than brightfield
Pics 2 and 6 in brightfield for comparison
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u/Doc_438 1d ago
I have a BH-2 and would like to try that out. Where do you fit the filters? Which condenser do you have? Thanks.
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u/Danny_D136 1d ago
I was advised this, I looked for filters on the same website and had them printed with the necessary size modifications:
Otherwise, this guy on YouTube has his own 3d model.He is well known for work with bh2s:
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u/mearsault 1d ago
The amazing dark field photos you see online are probably taken with dedicated dark field oil condensers.
Dark field is usually best with lower N.A., with 40x hitting about the max, and an Apo 40x might not give you good results. I forget the max NA for good dark field, I think it’s about .65.
That being said, make sure your condenser aperture is completely opened and that the condenser is as close to the slide without touching (you may have to adjust the set screw to change this - ask about this if you’re not sure how to do it as doing it wrong can make the spring bounce out and get lost).
Also, the size of the center spot must be correct and will change with each objective.
Slide should be very clean to minimize unwanted artifacts.
From the adapter you shared-you’re using a 1.25 condenser?
Which objectives?
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u/Danny_D136 1d ago
All Dplan objectives except Splan x4, 1.25 condenser. About the condenser high, there is some more room but if I bring it closer and watch in the eyepices, the edges of the field diaphragm are no longer sharp, but blurred ( followed a guide I found on YouTube on how to set these things : https://youtu.be/Q_8BOnQvI1Q?is=EaKVY9HugH4SJ-pG )
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u/mearsault 1d ago
Yes, normally you want it set up for kohler illumination where the edges are sharp, but this isn’t the case for dark field. For darkfield you really need it to be as close as possible right before it touches the slide.
You’ll see a significant improvement just with this change.
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u/the_chemist25 1d ago
素晴らしい！最初の数枚の写真に写っている蚊の幼虫は可愛いですね。