Fossil Aulacodiscus from St. Laurent (images added)
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Fossil Aulacodiscus from St. Laurent (images added)
I just finished cleaning a sample of raw diatomite from St. Laurent, France. There weren't many intact forms in the largest fraction (the material held back by a 175um mesh) but here's a nice Aulacodiscus reticulatus I picked out.
I'd hoped to get all details in a single picture, but it proved impossible even using a deep stack taken with a 40/0.95 planapo objective. The sharp detail of the pores kept obscuring the smoother overlying reticulation (which looks a bit like the skin of a cantaloupe).
I included 3 single-shot images taken at lower resolution with the condenser aperture closed down somewhat. This shows the reticulation more clearly, First inset is focused on the top of the valve, second halfway through and third near the bottom.
Guess it just goes to show you can't always capture everything in a single image, even with stacking, and particularly with transparent subjects like diatoms.
I'd hoped to get all details in a single picture, but it proved impossible even using a deep stack taken with a 40/0.95 planapo objective. The sharp detail of the pores kept obscuring the smoother overlying reticulation (which looks a bit like the skin of a cantaloupe).
I included 3 single-shot images taken at lower resolution with the condenser aperture closed down somewhat. This shows the reticulation more clearly, First inset is focused on the top of the valve, second halfway through and third near the bottom.
Guess it just goes to show you can't always capture everything in a single image, even with stacking, and particularly with transparent subjects like diatoms.
Last edited by Beatsy on Sat Dec 27, 2014 2:10 pm, edited 1 time in total.
- Cactusdave
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Really nice diatom find, and a fine image. The problem of trying to stack and display internal structure which is overlaid with a semitransparent, but structured surface is a perennial one. I have encountered it a lot with slide mounted small insects like bird lice.
Leitz Ortholux 1, Zeiss standard, Nikon Diaphot inverted, Canon photographic gear
- Wim van Egmond
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There should not be problem with the Zeiss oil dark field Ultracondenser 1.2-1.4, I use it with my 50/1.00 NPL FluotarWim van Egmond wrote:... But have to tried to photograph this subject with dark field? It may be hard with this NA objective but if you have an objective with an iris, or perhaps a lower NA objective.
Pau
Thanks all for the comments.
I had a look in darkfield, but it seemed far too "busy" or cluttered for that - overlying details obscured underlying ones even more. I could only use a 16x for that though. I used to have the ultra darkfield condenser, but it went missing during a house move. Two years on and I still occasionally search old boxes and obscure corners in the hope it might show up, but it never does
On an interesting side note, I found an old plate of diatom sketches that had two views of A. reticulatus drawn. One focused on the surface of the valve, one on the pores. From memory, I think it was a plate by Moller - so it seems I'm in good company with what appears to be a (very) long standing issue
I had a look in darkfield, but it seemed far too "busy" or cluttered for that - overlying details obscured underlying ones even more. I could only use a 16x for that though. I used to have the ultra darkfield condenser, but it went missing during a house move. Two years on and I still occasionally search old boxes and obscure corners in the hope it might show up, but it never does
On an interesting side note, I found an old plate of diatom sketches that had two views of A. reticulatus drawn. One focused on the surface of the valve, one on the pores. From memory, I think it was a plate by Moller - so it seems I'm in good company with what appears to be a (very) long standing issue
- carlos.uruguay
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Fossil Aulacodiscus from St. Laurent (images added)
Looks like "more NA" is the answer here. I oiled a planapo 100/1.3 and an NA1.4 condenser lens to the slide, added a touch of DIC and rattled off two stacks of the same diatom. The reticulation shows very clearly.
As I'd gone to the trouble of faffing with immersion oil, I took a stack from a large Coscinodiscus sp. mounted on the same slide (it's about 320um diameter). I considered these to be a rather "boring" genus, but was surprised at the level of extra detail that showed up. It's pretty much at the resolution limit of this setup, but I'm tempted to break out a deep violet filter and have another go with that. But too many new strews to search at the moment, so that will have to wait for a slow day
As I'd gone to the trouble of faffing with immersion oil, I took a stack from a large Coscinodiscus sp. mounted on the same slide (it's about 320um diameter). I considered these to be a rather "boring" genus, but was surprised at the level of extra detail that showed up. It's pretty much at the resolution limit of this setup, but I'm tempted to break out a deep violet filter and have another go with that. But too many new strews to search at the moment, so that will have to wait for a slow day
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Diatoms,
##### Beasty, these oil immersion stacks are off the charts. You dah man.
Mike
Mike
Michael Reese Much FRMS EMS Bethlehem, Pennsylvania, USA
- carlos.uruguay
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- Cactusdave
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The first of those shots with the oiled condenser is very very nice, just about as near to SEM as I've seen, and really on the edge of possible light resolution. Again I wonder if you have tried to make stereo pairs with these?
Leitz Ortholux 1, Zeiss standard, Nikon Diaphot inverted, Canon photographic gear