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UltravioletPhotography

Sea Shells, and Sea Swells


igoriginal

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Orange Beach & Gulf Shores, Alabama, USA

 

Some of my more recent trips to the shorelines of Gulf of Mexico beach areas (particularly, the beaches along the Alabama and Mississippi coast) has prompted me to consider: What does the beach scene, and all of its associated fauna and flora look like, under UV exposure?

 

Here are just a few preliminary comparison VIS and UV shots, though I plan to add more to this post, in due time.

 

 

- Camera: Panasonic Lumix G2 (full-spectrum converted)

 

- Lens: Soligor 35mm F/3.5 (Kyoei / Kuribayashi 35mm F/3.5 optical variant; 46mm filter thread, 23mm front element diameter, 11.5mm rear element diameter, M42-mount adapter over T-mount base), mounted on additional macro-extending helicoid tube (an M42-to-Micro 4/3 adapter with a macro extension-capable helicoid design).

 

 

- Settings for visible exposure: ISO 100, Aperture F/11, Shutter 1/125 sec., S8612 (2mm thick) filter, in-camera CWB (custom-white-balance) set to 18% neutral gray target, color-cast further corrected in post-photo editing.

post-34-0-03441900-1422337244.jpg

 

- Settings for UV-A exposure: ISO 100, Aperture F/11, Shutter 10 se., U-340 (2mm thick) and S8612 (2mm thick) filter stack, in-camera CWB (custom-white-balance) set to PTFE (virgin-white polytetrafluoroethylene / Teflon). Note: Late in the day, just an hour before sundown. Interesting, how the rendered UV-neutral colors of coastal vegetation varies, so abruptly, between shaded areas and areas bathed in late-afternoon sunlight.

post-34-0-86905300-1422337250.jpg

 

- Settings for visible exposure: ISO 100, Aperture F/8, Shutter 1/500 sec., S8612 (2mm thick) filter, in-camera CWB (custom-white-balance) set to 18% neutral gray target, color-cast further corrected in post-photo editing.

post-34-0-05307800-1422337272.jpg

 

- Settings for UV-A exposure: ISO 100, Aperture F/8, Shutter 1.6 sec., U-340 (2mm thick) and S8612 (2mm thick) filter stack, in-camera CWB (custom-white-balance) set to PTFE (virgin-white polytetrafluoroethylene / Teflon).

post-34-0-93567600-1422337278.jpg

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Nice work Iggy

I don't know how the green grass got through the filters ?

Col

 

Thanks, Col.

 

That's because nothing "got through." It really did appear golden-greenish under UV (whatever that sea vegetation was. "Sea oats", perhaps?)

 

I checked, and double checked, for any IR leaks, by using my set-up for other known and more common UV targets, and confirmed this.

 

Though, I have seen this phenomenon before (on occasion). Particularly in late-afternoon strong sun. ("Olive" or golden-greenish colorations, in specific types of vegetation). It remains a mystery to me, as to why this sometimes shows up. But, my under-educated assumption (without actually being able to test) would be that I suspect it may have something to do with changes in the ratio /bandwidth distribution of UV-A energy, when it comes to sunlight in the very late afternoon (just hours from sundown), but also still has to be very strong UV (such is the case where I live, here in the sub-tropical climate of the deep south USA).

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That's a good point. Could also be due to changes in the way the Bayer array / dyes react with certain distributions of energy; slightly altering the UV-neutral "white balancing" color response. Especially if one does not re-adjust the white-balance, as the sun moves into a different position in the sky (from mid-day, to late afternoon)???

 

Hmmm.

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Hello there Igor !! The sea shells are so interesting. Cool. Thanks for posting these.

 

****

 

False-greenish colours will often show up in a landscape UV photo made at any hour whereas in close-ups we usually don't see it too much. I don't really know why.

 

In addition to Igor's observation about UV variation w.r.t. time-of-day, remember that UV waves are short, bump into the atmosphere (very non-scientific phrase!) and get easily scattered so that could contribute to some differences between false colour in close and far photographs.

 

Somewhere recently I was listing all the variables which contribute to the false-colour effect. I need to go back and add distance from subject as a factor.

 

Added: Remember that sometimes our eyes 'read' a darker false-yellow as more of a greenish colour. False-yellow is not unexpected. I'll add my usual warning here about not over-interpreting false colours. :lol: :D

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Thanks all, for the input.

 

Thank you, Andrea, for that information.

 

Apologies, for not being on as frequently as this past summer ... however, I have some interesting UV and IR projects to present, coming soon. :)

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