Foraminifera from Timor

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enricosavazzi
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Foraminifera from Timor

Post by enricosavazzi »

Foraminifera sample from Timor (historic material in collections, from an expedition in the 1960s or 1970s), mostly planktonic but some benthic forams in the mix. Sony Aplha R II, Laowa 25 mm at 5x f/4, shot with MJKZZ Ultra Rail Mini, stacked with Zerene Stacker (DMap), background removed in Photoshop (mostly Magnetic Lasso tool). The background was a standard black plastic micropal well-slide, which as usual was full of very fine crystalline dust, and required complete masking away. The subject is shiny and mostly translucent white, with very low contrast. The 1:1 pixel crop shows some fine detail, in spite of not shooting at f/2.8 (which would display a little more detail). One pixel corresponds to 0.9 μm on the subject.
2022-07-29-07.41.39 ZS DMap masked S.jpg
2022-07-29-07.41.39 ZS DMap masked C2.jpg
PS - The 1:1 crop shows internal canals in the test* wall, visible through the translucent structure of the test wall. Most of the time, modern scientific publications on forams are illustrated with SEM images, which display surface detail with a resolution and DoF unattainable with optical imaging. However, SEM images do not show the internal test structure, which requires additional images of sectioned or broken tests, or time-consuming techniques like filling the test pores and canals with a resin and etching away the calcareous test material with an acid. Therefore, there is potentially a use for focus stacking in foram research, so far not so common in the modern literature because virtually all well-equipped research labs have an SEM. Traditional "single-shot" optical imaging is generally not used because the limited DoF makes the images unsuitable for illustration. Historic foram research solved this problem with hand-crafted illustrations, these days rarely used (except for simple, non-shaded line drawings) because of their high cost and potential for subjective "interpretation" of what the observer saw.

A few foram studies are illustrated with images from an optical scanning microscope (which could be regarded as a precursor of focus stacking), for example https://palaeo-electronica.org/2003_1/b ... enthic.pdf

* test is what the "shell" of forams is called. CF. the ancient "Testacea" term used for forams, and by extension even for mollusc shells in 19th century and earlier literature.
--ES

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