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UltravioletPhotography

UV Allamanda Flower in Sunlight with AstroDon UVenus filter


colinbm

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Hi Everyone

I have uploaded this file to DropBox, it is free. It is about 10mb.

https://www.dropbox....%20Sunlight.X3F

 

It is a Sigma .x3f file from a Sigma DP1 compact camera. Because it is an original (older) Sigma compact some propriety photo editor programs will open it, BUT it is best to open it with the Sigma Photo Pro RAW converter, convert it to a .tiff file & work it that way. I am a novice at PP & only use Sigma Photo Pro, I have next to no experience with the other editors.

Windows & Mac versions.....

http://www.sigma-dp1.com/software/spp/

 

I have some differently processed versions here too...

I haven't cropped these, to show the issues I having with this camera with a wide lens & the 1.25inch AstroDon UVenus.

The Sigma DP2 that I killed :lol: has a narrower field of view & I didn't have the reflection issues. I am looking for another DP2 to replace mine.

 

Mono conversion

post-31-0-78204000-1386059896.jpg

 

Blue / Black conversion

post-31-0-47912800-1386059957.jpg

 

Custom WB

post-31-0-44546700-1386060123.jpg

 

Straight jpg covversion

post-31-0-03673400-1386060243.jpg

 

Good luck & please share your results.

Cheers

Col

 

PS IMHO I strongly feel the pink / magenta cast is an artefact response of over-exposure, as the blue in it is clipped.

Col

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Col - Thank you so much for the raw file drop !!

 

Looking at the jpgs briefly that you posted, I note that the DP1 is creating some ring artifacts. This is from internal reflections off of something - inside of the lens?. I've seen this on occasion with one of my lenses. I don't know whether the ring "contamination" is from Visible, UV or IR light? (If that Astrodon UV-Pass leaks IR, then IR contamination is possible. The rings do appear lighter.)

 

Try using a lens hood. If you don't have one, create something simple from a cardboard tube. If a lens hood doesn't mitigate the ring reflections, then prolly the DP1 gets ruled out as a viable UV cam.

 

Here is a slightly lightened version of the first Jpg showing the rings.

post-31-0-78204000-1386059896.jpg

 

And a lightened verion of one of the color jpgs.

post-31-0-47912800-1386059957.jpg

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Thanks Andrea

I will be trying a bigger aperture today, to see if the aperture blades is where the reflections are coming from.

I can't wait to get the other camera back working again it has a narrower field of view.

Cheers

Col

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Again, thank you so much for sharing a raw X3F photo with us.

(And in the process reminding me about the Dropbox feature!)

 

I pulled the sample X3F file into Iridient Developer for conversion.

That is one very difficult file to work with !!!

I really got nowhere with attempted an white balance - or "rebalance" on this primarily monochrome file.

I think you already discussed this elsewhere - that a UV photo from the DP1would be primarily monochrome

because the shorter UV rays don't penetrate to the green or red Foveon layers.

 

It initially appears that the best UV photo from DP1 might be gotten via black & white conversions

with some work done to lift the shadows a bit. Just a tentative hypothesis for now.

 

The DP1 is recording a lot of detail for sure, so if you can get past all that false colour saturation

by either toning it down or going B&W there might be some nice stuff there.

 

Question:

(1) Do the DP cameras have a setting that opens up shadows while shooting? (On Nikon cameras this is called the Active D-Lighting setting. Other cameras have other names for it.) This would be useful I think for the UV work.

 

If you cannot pull shadows up in-camera while shooting, then practice increasing your exposure as far as you can to better expose dark areas. Later, highlights can be pulled back in the converter/editor. Naturally you have to be careful not to push the exposure so far that highlights are permanently blown.

 

(2) Do the DP cameras have a setting for B&W while shooting? Shooting UV subjects as B&W in-camera can be very useful for judging the underlying lumiosity (brightness) of the exposure because the misleading colour saturations are eliminated which can make the histogram appear as though it fully exposed when it is not.

 

I will play some more with the X3F file. :lol:

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  • 2 weeks later...

I an sorry Andrea, but somehow I missed your answer to this post :)

Thanks for looking over this file for me & your comments.

I will post another Allamanda flower with a Violet Blue Cyan Green filter about 380nm to 530nm, soon.

Yes I think the best details are in the B&W converted photos.

To answer you questions...

1. No, the Sigma DP cameras are bland simple. The Sigma Photo Pro raw converter program has a good 'fill light' adjustment. But I need to practice exposing for the shadows more.

2. Yes the Sigma DP cameras have a B&W setting in the menu. I will practice looking at the B&W histogram.

 

Cheers

Col

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