Darkfield Diatoms - Amscope Condenser on BH2

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josmann
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Darkfield Diatoms - Amscope Condenser on BH2

#1 Post by josmann » Tue Nov 30, 2021 2:31 am

Hey folks! I read in one of Carl Hunsinger's documents that the DK-DRY200 and DK-OIL200 condensers from Amscope were compatible and worked well with the BH2. I tried the dry condenser out today on my diatom test slide and really like the results!

Now, it should be said this is a bit more manipulated than I usually tend toward. It's meant to pop, not be faithful. I did a few things here: slammed the contrast and saturation to black out the background and brighten the valves, did a focus stack and composited with each diatom in the image I liked the best, slightly adjusted the diatoms so they're all perfectly lined up. Give me a minute and I'll post something that's a bit more faithful to the viewfinder so you can get an idea for the actual performance.

I also made a few phone wallpapers of this, they're posted on my reddit profile: https://www.reddit.com/user/DietToms/submitted/
diatomsprecropadjustedsq.jpg
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#2 Post by josmann » Tue Nov 30, 2021 2:48 am

Okay, here's a more faithful result trying to match the viewfinder (edited to match, no composition or stacking). This image was captured with an Olympus SPlanApo 20x objective (NA .70) and the dry darkfield condenser (NA 0.9). I also tried with a 40x SPlan (.70) - looks pretty similar, maybe a little darker? And a 40x SPlanApo (.95) - just looks like brightfield haha!

The background does not go completely dark under full brightness, but it is very even across the entire FOV and easy to subsequently darken in post or expose close to black in the camera. It absolutely works! Great accessory to pick up if you've got a BH2!
DSC07836real.jpg
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#3 Post by deBult » Tue Nov 30, 2021 2:57 am

Nice work, thanks for confirming the Amscope DF compatibility to the BH2.

Any chance on testing the oil version (expect it may match the na 0.95 objective) ?
(BH2 user here and already have and use the Oly dry dark field condenser).

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#4 Post by josmann » Tue Nov 30, 2021 3:07 am

deBult wrote:
Tue Nov 30, 2021 2:57 am
Nice work, thanks for confirming the Amscope DF compatibility to the BH2.

Any chance on testing the oil version (expect it may match the na 0.95 objective) ?
(BH2 user here and already have and use the Oly dry dark field condenser).
Yeah, definitely! I've got the 100x oil SPlanApo too so we'll see if I can get that to go dark as well :D

I'm super behind on videos for my youtube peeps though so I have to work before I can do any more play :lol:
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#5 Post by Hobbyst46 » Tue Nov 30, 2021 3:08 pm

The Zeiss 100X1.3 Planapo does not yield DF because that NA is too high.
I manage to get imprefect DF with an old 100X1.25 achromat, perhaps because its front lens metal cover functions somewhat as iris.

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#6 Post by josmann » Tue Nov 30, 2021 8:52 pm

deBult wrote:
Tue Nov 30, 2021 2:57 am
Nice work, thanks for confirming the Amscope DF compatibility to the BH2.

Any chance on testing the oil version (expect it may match the na 0.95 objective) ?
(BH2 user here and already have and use the Oly dry dark field condenser).
Hobbyst46 wrote:
Tue Nov 30, 2021 3:08 pm
The Zeiss 100X1.3 Planapo does not yield DF because that NA is too high.
I manage to get imprefect DF with an old 100X1.25 achromat, perhaps because its front lens metal cover functions somewhat as iris.
Okay so oil was a bit more of an adventure. When I placed the oil condenser in the BH2 mount, it did not seat properly. It floated around the condenser mount and could not be locked in place. After some investigation, I noticed that the condenser I received has a completely different dovetail than the DK-DRY200:
IMG-7998crop.jpg
IMG-7998crop.jpg (90.67 KiB) Viewed 4094 times
The upper radius is smaller and the chamfer at the edge is not present. I am fairly certain this is just the wrong model condenser. This is not too surprising considering the packaging was worse than many eBay optics I've received! I have no idea how they can pass this off as professional order fulfillment. Two of the items in my order - the DK-SRY200 and the immersion fluid were just burrito-wrapped in a cut out section from a padded USPS envelope secured with packing tape. The oil condenser came in a padded box with old yellowed foam that I don't believe can be the original packaging. And it all came loose in just a padded yellow envelope. I swear Amscope's quality of service oscillates between incompetent and ambivalent...

Anyway, I believe the condenser is still optically pretty much the same and I was indeed able to get it aligned beneath the oil objective with a bit of care. Using the iris on the SPlanApo 100x turned about halfway down I was able to achieve a darkfield effect that was much darker than the dry condenser (perceptually black background through the eyepieces!) with good, aberration-free images of the frustules. I took some photos but I haven't gotten through processing them. I will post a new thread once I get something I'm happy with. So yeah, assuming you win the Amscope order fulfillment lottery and get what you ordered, I think the oil condenser is an easy recommendation as well!

I also noticed that for lower numerical apertures, it lit the diatoms distinctly differently. So you can get different effects by using it in place of the dry condenser.
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#7 Post by deBult » Tue Nov 30, 2021 9:24 pm

Tnx for the update.

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#8 Post by Javier » Tue Nov 30, 2021 11:50 pm

Very nice images and good editing skills. Thanks for sharing!

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#9 Post by apochronaut » Wed Dec 01, 2021 1:14 pm

Good results. Often DF images can be plagued by extreme contrast with a kind of corona around the subject matter. The problem with the dovetail fit is the main problem when adapting DF condensers across brands. That and height. Height can often be easily adjusted for and many older condensers are height adjustable.
Optically, there is no reason why any DF condenser will not work on any microscope with an understage illuminating window.

Whether the microscope has enough illuminating power so a bright enough image can be seen or whether the objective being used has the requisite -20 or more N.A. in order for DF to take place are other issues that exist when any DF condenser is used whether native or off brand.

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#10 Post by smollerthings » Wed Dec 01, 2021 4:06 pm

Very nice. I hope to see DF stunning pond videos soon!

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#11 Post by josmann » Wed Dec 01, 2021 6:13 pm

apochronaut wrote:
Wed Dec 01, 2021 1:14 pm
Good results. Often DF images can be plagued by extreme contrast with a kind of corona around the subject matter. The problem with the dovetail fit is the main problem when adapting DF condensers across brands. That and height. Height can often be easily adjusted for and many older condensers are height adjustable.
Optically, there is no reason why any DF condenser will not work on any microscope with an understage illuminating window.

Whether the microscope has enough illuminating power so a bright enough image can be seen or whether the objective being used has the requisite -20 or more N.A. in order for DF to take place are other issues that exist when any DF condenser is used whether native or off brand.
Thanks Apo. Yeah the Amscopes generally seem to come with a 37mm mount or a 42mm mount. The BH2 is a 42mm so I assume the oil one I received is a 37. And I definitely get a "bright enough" image with the halogen bulb on the BH2 but it could be brighter for sure. I have to turn my camera ISO up from around 100-200 typically to 1000 or so. Still perfectly usable, but it's noticeably dimmer. The toroidal aperture on the oil condenser is only about 8mm in diameter with a 1mm thickness. Not much light collecting area!

On the subject of the corona, I've definitely noticed that high mag DF is definitely difficult with thicker specimens. Is the corona just spherical aberration being made more visible with the higher contrast?
smollerthings wrote:
Wed Dec 01, 2021 4:06 pm
Very nice. I hope to see DF stunning pond videos soon!
I've got the green hydra video up! I think I'm definitely going to need to work on my specimen prep to get good DF videos. Slide clarity and cleanliness is SO important and having a lot of stray detritus is also not good.

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#12 Post by smollerthings » Wed Dec 01, 2021 6:19 pm

That is one good looking hydra. :D

What objective was this?

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#13 Post by josmann » Wed Dec 01, 2021 6:27 pm

smollerthings wrote:
Wed Dec 01, 2021 6:19 pm
That is one good looking hydra. :D

What objective was this?
Thanks! I just found them in an old sample jar that rarely ever yields anything interesting. They're all over the place!

First objective is 4x, then switched over to the 10x. Both are SPlanApo. This is with the dry condenser and a deep well slide.
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#14 Post by smollerthings » Wed Dec 01, 2021 8:07 pm

How does the 40x look with the dark field condensers? I never could get anything 40x with the Abbe (I think it is normal, the NA of the objective is too high)

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#15 Post by josmann » Wed Dec 01, 2021 9:44 pm

smollerthings wrote:
Wed Dec 01, 2021 8:07 pm
How does the 40x look with the dark field condensers? I never could get anything 40x with the Abbe (I think it is normal, the NA of the objective is too high)
The 40x SPlanApo needs the oil condenser but it works just fine. The dry works perfectly well with 40x objectives of NA .70 or less.

When you get to higher mags, the precision of the darkfield conditioning matters more. The annulus in the Amscope dry objective is a very thin aluminum piece with a dot diameter of 20mm. I imagine it's positioned exactly at the focal point of the optics but I don't think the optics themselves are too much different from an abbe condenser.

One protip for ya is you can install filters in your Abbe condenser by dropping them inside and closing the aperture blades slightly to create a shelf. Then use your finger to finely adjust the position and install it without knocking it around too much. This will position the annulus optimally for a sharp cutoff of low angle rays. I was able to achieve very similar performance just now by removing the annulus from the Amscope condenser and installing it in a standard Olympus Abbe condenser as described. I had to decenter it a little bit to get away from a bright zone, but honestly it was hard to tell the difference after that!
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#16 Post by josmann » Wed Dec 01, 2021 11:00 pm

How about one more? I gotta give smollerthings some credit for this one - I stumbled upon this while trying out the method I described above. With an annulus installed in a standard Olympus Abbe condenser, the field iris stopped all the way down, and a bit of condenser position tweaking, I was able to cast a nice rainbow over my diatoms :)
rainbow diatoms sq sm.jpg
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Re: Darkfield Diatoms - Amscope Condenser on BH2

#17 Post by smollerthings » Thu Dec 02, 2021 10:08 am

josmann wrote:
Wed Dec 01, 2021 9:44 pm
dropping them inside and closing the aperture blades slightly to create a shelf. Then use your finger to finely adjust the position and install it without knocking it around too much.
Interesting method, will try. Thanks ;)

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Re: Darkfield Diatoms - Amscope Condenser on BH2

#18 Post by carlh6902 » Mon Nov 06, 2023 4:48 pm

Here is a usable way to add darkfield and oblique to your BH2 (BHT, BHTU, BHS). The darkfield results will not be as good as what you can obtain with the true darkfield condensers discussed in this thread, but is certainly acceptable.

https://drive.google.com/drive/folders/ ... drive_link

https://drive.google.com/drive/folders/ ... drive_link

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--- If you're in the Kansas City area and you need help with an Olympus BH-2 scope, PM me. I love to work on these things ---

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