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Photographing fluorescence

Posted by Dennis McCoy  
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Dennis McCoy December 01, 2014 11:01PM
I have been playing around with photographing fluorescent minerals, and have found more than I anticipated, thanks to a new blacklight. Is there a best setting for this? I am using a Canon powershot S2 IS. The following are unretouched, just resized to fit here.

calcite with selenite (left) Dolomite psuedo of aragonite(upper right) and Calcite after glauberite.


Calcite from Mexico


Quartz geode from Mexico with fluorescent mineral frosting.
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Doug Daniels December 02, 2014 01:18AM
I'm sure there are other threads on this subject, as well as info on the fluorescent mineral society's site (I forget the url). Two things - don't put a white background behind the specimen (it will reflect the UV back to the camera, or at least fluoresce - guess how paper and clothing brighteners work?); and, I think even with digital cameras, you need a UV filter (not a skylight filter).
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Dennis McCoy December 15, 2014 12:42AM
Doug, thanks for the tip about the dark background. It helps the camera recognise the exposure needed.
Now with a timed exposure I am getting better photos.

here is a group of fluorites.


Same shot with a red filter to kill the blue visible light, leaving only the fluorescence.


Still another fluorite with fluorescent calcite.
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WaterDog December 19, 2014 06:13PM
To remove some of the blue you can try changing the white balance for the camera. For my cameras, I find that a color temperature of 7000K works well. I don't think the Canon Powershot S2 IS supports specific color temps, so maybe try the "cloudy day" setting for white balance or try the "custom" setting using a piece of white paper under your UV light as a calibration target. Position the UV light at about the same distance from the paper target as you hold it from the specimens.
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Ronald J. Pellar December 19, 2014 06:49PM
Watch out! Most white paper has fluorescent brighteners. Custom white balance should be done with a spectrally flat gray card.
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Harold Moritz December 19, 2014 08:36PM
Most UV lamp filters bleed way too much blue light, hence your very blue photos, and the camera tends to be more sensitive to the blue light than your eyes. Dont use a red filter as you will cut out some fluorescent response. You can set color temp as described above and use a Haze 2A filter. But I end up using Photoshop to take out some blue, while viewing the specimen fluorescing on the table next to the computer to get the color balance just as my eye sees it. Also, do not overexpose the fluorescing minerals. They are light sources, so they can saturate the sensor very quickly. Best to take 2 or 3 images with different exposure times and pick the best one that shows detail not just blazing color.
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Chris Clemens December 20, 2014 12:04AM
Dennis,

There is some good info in the responses above. In my experience photographing fluorescent minerals, here are a few techniques that have worked for me:

1. A good tripod is mandatory. The camera needs to be rock-solid steady during the exposure to ensure maximum sharpness.

2. As Doug mentioned above, use a black background. A piece of black cloth, velvet, or felt works well.

3. Fill the image with your subject and minimize wasted background space. To do this, most specimens (especially smaller ones) will require the use of the macro setting (button with flower) on your camera.

4. Use a small lens aperture (high f number) and a longer shutter speed during your exposure. The small aperture will provide the greatest depth of field and sharpest image. I typically shoot at f 8 with an exposure time of around 3 seconds, but the best exposure will always be dependent on the intensity of the fluorescent response.

5. Brighter-fluorescing subjects will typically photograph better than dimmer-fluorescing specimens. With some dimmer-fluorescing pieces, you may end up photographing more blue lamp shine than actual fluorescent emission. This seems to be especially true for long wave specimens. Beware.

6. As Harold mentioned, Photoshop (or similar software) can be useful for correcting color balance and/or exposure if necessary. It is also useful for cleaning up the background of the photograph (removing fluorescent lint, dust specks, etc.).

I have attached an example of a recent photograph that I shot of a specimen of calcite, chondrodite, diopside and aragonite from the Long Lake Zinc Mine in Ontario, Canada. Illumination was provided by a 6 watt, short wave lamp (254nm), and the exposure was 3 seconds at f 4.6 at an ISO setting of 200.

Hope these tips help. I have found the photography of fluorescent minerals to be quite addictive!


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