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UltravioletPhotography

Fragaria vesca [Wild Strawberry]: UV Anaglyph


bvf

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Foot, Bernard (2020) Fragaria vesca L. (Rosaceae) Wild Strawberry. Flower photographed in visible and reflected UV light together with UV Stereo Anaglyph.

https://www.ultravio...ry-uv-anaglyph/

 

Location:

Date: 28 April 2019

 

Reference:

1. Wikipedia (29 June 2021) Fragaria vesca. Wikimedia Foundation, San Francisco, CA.

2. Fitter, R., Fitter, A. and Blamey, M. (1996) Wild Flowers of Britain and Northern Europe, 5th Ed. Wild Strawberry, page 116. HarperCollins Publishers, London, U.K.

 

 

 

Visible Light

post-245-0-00402800-1585398169.jpg

 

 

Ultraviolet Light (Baader U, flash):

post-245-0-20591300-1585398180.jpg

 

 

UV Stereo Anaglyph

post-245-0-21409000-1585398197.jpg

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Thanks, Birna.

 

I guess there are 2 aspects to talk about - (1) doing the close-ups, and (2) creating the stereo anaglyphs.

 

In terms of the close-ups, my normal macro lens that i use for the visible images isn't UV-capable. So I have to use my favourite UV-capable lenses (Cassar S 50mm/f2.8, El Nikkor 105mm/f5.6) with extension tubes and bellows. The El Nik is better in terms of providing more working space in front of the lens, but focussing is tough because of the small aperture. I use 4 flashguns for illumination, as close to the subject as I can get them. This is no good for focussing, and I do have an Exo Terra lamp to help with focussing, but it's not really bright enough.

 

However, the focussing issue is really addressed by having to use focus stacking to get enough depth of field. I set the starting point in front of the subject using visible light, and then add the UV filter (Baader U) and do the focus stacking sequence, graduallymoving the focus further away until I can see in the captured images that there is no longer any part of the subject in focus. I don't have any automated focus stacking kit, so this is all done manually. Using something like a focussing ring is too coarse to get a good stack, so I normally move the whole camera and lens assembly forward on a slider. This probably shouldn't work because the lens is moving towards the subject all the time and so it's point of view is changing - but it does seem to work OK. I use Zerene stacking software.

 

I always work with the lens set to f/8 because that's the sweet spot for pretty well every lens I have used in terms of image quality. However, I suspect that rule of thumb probably doesn't apply when you're using bellows, because the effective aperture is lwss than the marked aperture. And certainly I suffer from flare and reduced image quality as the magnification increases.

 

Turning to getting the stereo shots, of course you have to make a left and a right image. Just moving the camera sideways between the two shots doesn't work well for macro and near-macro work, because even very small camera movements mean that your left and right images don't overlap. So the technique I have ended up using is to make my right-hand focus stack, then swing the camera through 5 degrees clockwise (when viewed from above) and move it sideways left on a slider until the subject comes back into frame. Then do the left-hand focus stack. If you look at books, etc., about stereo photography they tell you that you must not toe-in in this way. But I think that must be from the days of film because your two images would have a different perspective and would not line up. However, this technique seems to work well in the digital world - I combine my two images using a bit of free software called Stereo Photo Maker, which works beautifully.

 

There are various rules about how you can change the alignment between the left and right images, for example to make the subject appear to be coming through your PC screen - but if you break the rules you can get unpleasant effects. If you use software like Stereo Photo Maker it will always give you an acceptable result.

 

Hope this all makes sense - let me know if you have any questions.

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Thank you for the extra information. Very useful information that helps explain the excellent image qualities of your latest posts. You must be patient to work in this disciplined manner for sure.

 

I'm more impatient thus use Stackshot automation myself. With my Broncolor studio flashes (uncoated Xenon tube) light is never a problem exposure-wise, but I do have to be careful lest the flower should start to wilt from the flash-generated heat. Sometimes, in particular with smaller flowers, I "float" them in an aluminium block with a large water-filled hole in it. That helps dissipating the heat quickly. Also I try to stop down a little more in order to reduced the length and duration of the stacking process. One has to find an optimised balance.

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Yes, flower movement (wilting, "twitching" of petals and stamens, etc.) is a problem when you're doing large stacks (doubled up for stereo) - lots of images have been ruined by this, and there are some flower types - inc. Dandelion - which my techniques don't work with as a result.
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Bernard, how do you set up the 4 flashguns? Are they on some kind of tripods or what? Thank you.
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Yes, they are on tripods. I use 2 tripods each with one of these flash brackets or similar: https://www.ebay.co.uk/itm/1-4-Screw-Tripod-Light-Stand-Holder-Flash-Bracket-Mount-Adapter-For-DSLR-Camera/153079403775?epid=2171433792&hash=item23a43e54ff:g:RwgAAOSwzgRWytmU

 

Then I use cold shoes like these to mount 2 flashguns to each bracket: https://www.ebay.co.uk/itm/2-Pack-Cold-Shoe-Bracket-Adjustable-Metal-Cold-Shoe-Adapter-Mount-For-Dslr-C-2H2/303138624831?hash=item469478553f:g:OHcAAOSwqghcxosG

 

It does get a bit busy with with 9 tripod legs vying for floor space!

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Thank you for this info about tripods and the cold shoes. I've been trying to decide how to set up my 3 flashes.
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