• Ultraviolet Photography

Golden Columbine (Aquilegia chrysantha)

Fluorescence Infrared Multispectral
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#1 Mark


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Posted 09 April 2019 - 10:39

In this multispectral set there are two lessons learned, one on the application of a UV diffuser, and the other on IR illumination. Let's get right to it, starting with a wide VIS shot of my subject, for reference.

Today's subject is a Columbine (Aquilegia chrysantha). Yes, it has its own Wikipedia page, albeit brief.
Attached Image: 2019-04-07_18-37-48__abr800--s8612-420lp.jpg

The first lesson I take from this set is: Do NOT use a diffuser on my UV source. Unfortunately, I only figured this out after shooting practically the entire set. Judging from this with- and without-diffuser comparison, it's rather clear that the diffuser is not only reducing the focus of the UV source, but also its intensity and perhaps wavelength. Both images here were developed together with equivalent adjustments, showing an obvious difference in luminosity and fluorescent chromaticity.
Attached Image: 2019-04-07_18-24-22__mte-u340-dif--baader-489.jpg

In this reflected UV view the sepals look sandpapery, while the petals appear inky and metallic. And though it's hard to say for sure, because I didn't purposefully illuminate for it at the time, it appears the petal spurs may also be very UV dark.
Attached Image: 2019-04-07_18-12-27__mte-u340-dif--0340.jpg

Back to VIS here, but up close and personal this time.
Attached Image: 2019-04-07_18-06-21__amb--s8612-420lp.jpg

While I like that little blue light at the base of the stamens, what is interesting to me in this UVIVF view is how brightly fluorescent the damaged tip is of that one sepal on the right (due to pooling of fluids at that point perhaps?)
Attached Image: 2019-04-07_18-09-03__mte-u340-dif--baader-489.jpg

Some very subtle false color and IR fluorescence in this UVIIF view.
Attached Image: 2019-04-07_18-00-58__mte-340-dif--r72-yk2.jpg

There is much greater fluorescent contrast in this CyIIF view. For this entire set I can't decide if I like this or the UV image better.
Attached Image: 2019-04-07_18-02-40__cyanled-bg39--r72-yk2.jpg

The other learned lesson I take from this set is to use highly diffuse/ambient IR illumination, as in this image. The bare bulb flash used here was reflected off a wall at the opposite side of the room. This allowed for developing higher contrast in the resulting image, without a high degree of burning either highlights or shadows. And from that, the translucence in the sepals is now more pronounced, making the internal structures more evident; notably as compared to the petals. This one of the first IR images I've liked in my multispectral sets in a long time.
Attached Image: 2019-04-07_18-19-15__abr800--r72-yk2.jpg

- Mark

Edited by Mark, 09 April 2019 - 17:30.

#2 dabateman

    Da Bateman

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Posted 09 April 2019 - 23:04

Which diffuser did you use?
I will have to test the Lee 750, to see if I see similar. So far that would be the best diffuser.

#3 Mark


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Posted 10 April 2019 - 13:04

I used a Roscolux #163. To be clear, the diffuser worked well enough for the UV image, but the loss of UV intensity for exciting fluorescence was unacceptable. And in the end it's not really much of a benefit to me to have the UV source diffused for UVIVF images, pointedly because I've become accustomed to light painting my subjects anyway. So... good for UV images - not so good for UVIVF images.