Thin Section Enlargements

I've been asked to scope out a project, that would involve the creation of large (approximately 1 meter across) color "art" (and science) prints from petrographic thin- section slides (i.e., standard 30-micron thick rock sections, mounted on 27 x 46 mm. glass slides). The detail would need to be sufficient to show surface details on sand grains, with a field of view of about 5 mm (i.e. what you would see looking through a microscope at about 20-40 times magnification). Polarizing filters would be needed to distinguish different mineral fragments.

So far, people I’ve talked to, who are familiar with photomicrography (including myself to some degree), are concerned about the results of images taken through a petrographic microscope with transmitted light, where the enlargement of blurry edges of rounded grains, and distractions from features on the back of translucent grains interfering with foreground features, are liable to be glaring at “poster size�. Digital “sharpening� programs like Helicon could be used to solve some of the depth of field problems for digital images, but pixellation could be a noticeable distraction at high enlargements.

One option I have heard of is to put a slide directly into a high-resolution slide scanner, with 2 layers of polarizing film, and then enlarging that. That eliminates some of the optical problems coming from intervening lenses, and sounds like maybe a good way to go, but I’m not sure of the trade-off in resolution once that image is blown up, or how much it resolves depth-of-field issues (though it sounds like it would help a lot).

Has anybody seen a successful project like this, and have any tips on which way to go or where to look? I’m afraid the people I’m looking into this for are expecting “Ansel Adams�- type images and may be disappointed at something far less attractive. I’m not sure what the current state-of-art is on this. There are lots of great microscopic images in magazines and on the internet, but a large framed print, hanging in a gallery or museum, is another thing entirely.

You really don't end up with surface details on sand grains in thin sections (except looking at the edges).

Some older research scopes had larger format cameras (for polaroids). Scanning those might result in images that could be blown up.

There is a reason Adams used a large format camera.

If you look at what Mineralogical Record recommends for photographs that they print, it is 300 dpi. For a meter wide print that would require approximately 12,000 pixels. For screen resolution, that is still 3000 pixels.

Would this level quality be useful?

[www.mindat.org]
[www.mindat.org]

Thanks, David. Your first point is of course correct, and reminds me how long it's been since I actually studied a thin-section. And, even if you could see them, the surface details in the middle of the sand grains are liable to be ground down anyway in the preparation of the thin section. As to the large format Polaroid, I hadn't thought of that, and it’s one place to look. As far as the dpi needed, your examples are helping me see the limitations of digital equipment (while attempting to keep in mind that a pixel is not the same as a dot). .

And Daniel, those images are really striking. May I ask what equipment you used?

I perhaps should confess that the people who were originally asking me about this are some petroleum-types, who mainly want to see the beauty in a sandstone reservoir with unusually high porosity. I know that’s not what this site is about, but at least there are some smart people here.

Hi Kelly
I have a friend who does alot of contract work for mining companies and has experimented with polarising sheets and high quality bench scanners, the results they have had are very good.

I can't give you the specifics, as it wasn't my project! But even using standard benchtop pc scanner I remember we were all surprised by the results they achieved..some really nice shots.

Mike

Thanks, Mike. I was thinking of giving that very thing a try this morning, and after seeing your message, I'm motivated to give it a shot. I'll report back on what I come up with, though it may take me a few weeks to assemble all the pieces and tinker with it.

-Kelly