Diatom stacks

Beatsy · Post by **Beatsy** » Sun Sep 25, 2016 1:14 pm

Pun intended.

I had major problems with glare on these. Didn't help that the diatoms were near the edge of coverslips which had to sit right in front of the lens (13mm working distance on a 50x mitty). Other diatoms in front of and behind focus made things even worse. Ended up with horribly low contrast images that needed serious levels adjustment in PS. the final images aren't that good but show the idea. Seemed a shame to waste the effort, so you get to suffer them too

I've got some plans to improve things but taking a break from these for now as the stacks were mondo deep (600-800 images apiece). Consider these a work in progress and (hopefully) a prelude to better ones another time. Maybe.

Lou Jost · Post by **Lou Jost** » Sun Sep 25, 2016 3:00 pm

It's actually quite nice to see them on edge like this!

ChrisR · Post by **ChrisR** » Sun Sep 25, 2016 4:14 pm

Coo - I've never seen views like those.

Saul · Post by **Saul** » Sun Sep 25, 2016 10:14 pm

Very interesting result. What lightning setup was used ?

g4lab · Post by **g4lab** » Sun Sep 25, 2016 11:30 pm

WOW!!

Beatsy · Post by **Beatsy** » Mon Sep 26, 2016 12:23 am

Saul wrote:Very interesting result. What lightning setup was used ?

A single 10w LED panel (Trond lamp) angled in from top right with a white reflector on the opposite side for a (very) small bit of fill. The latter probably wasn't necessary as given a handful of photons diatoms tend to efficiently spread them around anyway.

Beatsy · Post by **Beatsy** » Mon Sep 26, 2016 3:13 am

Fixed it! A round headed bolt, small coverslip, black nail varnish and circular polariser (not shown) all contributed to improvement. Contrast was great and flaring minimal. I won't go into details as this is the wrong section of the forum - but here's a diatom taken with the improvements in place and a pic of the setup (along with detritus that fell on the coverslip overnight).

Dead simple fix(es) really. The glass is a bit too reflective now as you can't see what the diatom is resting on (note: it's not glued, just static holding it on-edge like that). A few light scratches with emery paper might fix the 'invisible surface' though. Next time...

leonardturner · Post by **leonardturner** » Mon Sep 26, 2016 4:13 am

Spectacular!

Cactusdave · Post by **Cactusdave** » Mon Sep 26, 2016 4:20 am

Superb and innovative. That last shot is a classic. I've done various diatom 'edge ons' from conventional thick strews, but nothing as clear and clean as this. Not having a coverslip on top really helps. Responding to this thread and your other one on Isthmia, I think there is something to be said for incident (epi) lighting of diatoms, or mixed incident/transmitted light even with a conventional coversliped mount. I have had some nice diatom results with the Leitz Ultropak epi attachment and its matched epi objectives on my Leitz Ortholux. Some examples in this thread http://www.photomacrography.net/forum/v ... 847#112847

Lou Jost · Post by **Lou Jost** » Mon Sep 26, 2016 5:44 am

Beautiful!! Congratulations on tracking down and solving all the problems!

Was the polarization done with a single polarizer on the light source, or crossed polarizers?

JH · Post by JH » Mon Sep 26, 2016 8:50 am

Nice, new and inovative

Regards Jörgen

Pau · Post by **Pau** » Mon Sep 26, 2016 10:18 am

Outstanding project and brilliant results!, nice to see your setup

I would never have thought to do this approach with diatoms, even less with a moderate aperture objective

Beatsy · Post by **Beatsy** » Mon Sep 26, 2016 11:20 am

Thanks for the comments everyone.

Dave: you've got some really nice images on that link. I got frustrated with deep stacks of mounted diatoms though. Soon as you get more than (say) 50µm into the mountant, lens aberrations start to kick in. I've lost count of the number of times I've tried to stack a nice fat Auliscus (one of my favourites). All the nicely tilted ones came out naff - only face on (therefore not too deep) worked well.

Lou: Just a single circular polariser acting as a "shade" between light source and subject. Set quite close to the subject to block unfiltered light.

Pau: I wasn't sure it would work really, but after resolving pretty small details in butterfly scales I figured large diatoms with chunky features should do OK. This has been on my "meaning to try" list for ages - mainly because of the issues with mounted diatoms described above. The 50x mitty was the enabler, but now I'd like an N.A. 0.75+ epi objective with at least 8mm working distance. Preferably around 64x or less. Fat chance

Cactusdave · Post by **Cactusdave** » Mon Sep 26, 2016 12:26 pm

Thanks Beatsy.

now I'd like an N.A. 0.75+ epi objective with at least 8mm working distance. Preferably around 64x or less. Fat chance

I thought at first that this might suit you, but the NA is no better than the Mitty. Long working distance and high NA just don't go together. https://www.micro-shop.zeiss.com/?p=us& ... 2-9960-000 and you might need an even bigger mortgage to get one.

Pau · Post by **Pau** » Mon Sep 26, 2016 2:09 pm

...but now I'd like an N.A. 0.75+ epi objective with at least 8mm working distance. Preferably around 64x or less.

Me too...if the price is reasonable

I have a nice 40/0.80 Plan Apo metallurgical with no much use because the minute WD, will try it in the future if I find suitable diatoms. Following Cactusdave, LWD and high NA....Is good to dream