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UltravioletPhotography

Sony a7R, UV and Aerochrome sim Black-eyed Susans


GaryR

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It's been an interesting ride with the foveon sensor, but I'm back to a Bayer sensor on the Sony a7R (no diagnostic IR LED in this model). I'm glad to see that the a7R can easily produce color UV (with the Andrea U), something that the Sigma Quattro was unable to do. The colors in the Sony Aerochrome simulation, turned out to be very similar to my old Sigma DP1.

 

Black-eyed Susans (Rudbeckia hirta)

Sony a7R FS-conversion, Nikkor 50/1.8 + Andrea U

manual WB, f/5.6, 1/10s, ISO 1600, +1.7Ev

post-189-0-76200100-1534983159.jpg

 

Black-eyed Susans (Rudbeckia hirta)

Sony a7R FS-conversion, Nikkor 50/1.8 + Yellow #12-XNite CC2 stack

manual WB, f/4, 1/40s, ISO 100

post-189-0-61687400-1534983197.jpg

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Gary, What is your reasoning behind stacking the CC2 with the #12 filter?

 

By the way, for comparison, in case anyone wonders,

MaxMax CC1 and CC2:

330-cc1-cc2_Medium.jpg

 

 

Compared to,

Schott KG1 2mm and BG38 2mm:

post-87-0-56195500-1534999742.jpg

 

 

And here is a Schott OG515 2mm + KG1 2mm stack.

Tiffen #12 has 50% T (520nm) half way between OG515 and OG530, so I am using 515nm here, either should be close to the same as #12.

post-87-0-80947800-1535002685.jpg

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You mentioned the Sigma Quattro in your post as not being suitable for colour UV. Do you know how it performs for UV generally? Sigma lent me one to try out but I could not find an adapter to fit my "UV" lenses on to it. With a user removable hot mirror filter it could be very attractive for some users. Sigma themselves do not know!
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Nice pictures!

 

I would have thought the UV pattern on the rudbeckia would be darker? Does it vary by species maybe? Or does AndreaU let through some visible?

http://www.ultraviol...ack-eyed-susan/

 

Thanks Andy!

This was an 'on-the-fly', handheld shot, taken in the shade, so there's definitely room for improvement on my part. The Andrea U does have some visible leakage, so not as dark and contrasty as the Baader U. Here's a example and comparison of the Baader U / Andrea U on Dr. Klaus Schmitt's UV site.

http://photographyoftheinvisibleworld.blogspot.com/2011/11/uv-baader-u-versus-andrea-u-filter.html

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Gary, What is your reasoning behind stacking the CC2 with the #12 filter?

 

By the way, for comparison, in case anyone wonders,

MaxMax CC1 and CC2:

330-cc1-cc2_Medium.jpg

 

 

Compared to,

Schott KG1 2mm and BG38 2mm:

post-87-0-56195500-1534999742.jpg

 

 

And here is a Schott OG515 2mm + KG1 2mm stack.

Tiffen #12 has 50% T (520nm) half way between OG515 and OG530, so I am using 515nm here, either should be close to the same as #12.

post-87-0-80947800-1535002685.jpg

 

Thanks for posting CC1/CC2 graph. I came across this article, detailing a method of accurately simulating Kodak Aerochrome film, with a Sony a7R II. In this tutorial, a Kopp 7093 filter is used (with a yellow #12), to match the spectral characteristics of Kodak Aerochrome film.

 

https://www.nickspiker.com/blog/search-digital-kodak-aerochrome/

 

I don't have any Matlab skills, but willing to try the suggested filter, using my own processing techniques. The CC2 is slightly beyond 900nm, used on the Kopp 7093, and thought it might be close enough to work. With only the yellow #12 filter, the final results have a lot of purple, whereas adding the CC2 seems to add color definition and more EIR-like reds to the image. I don't know of any standard 52mm filters, that would be similar to the Kopp 7093, but the CC2 does make a difference.

 

http://www.koppglass.com/filter-catalog/ir-infrared-filter-glass.php

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I love the contrasts (and composition) of the 2nd photo. Good one!

 

The AndreaU changes from version to version. Earlier models passed more violet. Gary, I suspect that you have an earlier model AU, yes?

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You mentioned the Sigma Quattro in your post as not being suitable for colour UV. Do you know how it performs for UV generally? Sigma lent me one to try out but I could not find an adapter to fit my "UV" lenses on to it. With a user removable hot mirror filter it could be very attractive for some users. Sigma themselves do not know!

Hi Adrian, The sd Quattro that I had performed amazingly well for monochrome UV. The 3-layer foveon sensor concentrates UV sensitivity in the blue layer only, and IR in the red layer only. There's a hint of UV/IR sensitively in the green layer, but unusable for the most part. Yes, the removable dust protector/ hot mirror filter is an attractive feature, but unfortunately the sd Quattro is the only Sigma dslr model with 'live view' and an EFV. All other SD dslr models only have an optical VF, and an LCD screen which is only used for shooting info, and image review. I got into Sigmas, because of their ability to record Aerochrome-like, red foliage images, SOOC. Unfortunately, the latest design of the Quattro foveon sensor, can't match the lush reds and pinks of the original DP* series.

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I love the contrasts (and composition) of the 2nd photo. Good one!

 

The AndreaU changes from version to version. Earlier models passed more violet. Gary, I suspect that you have an earlier model AU, yes?

 

Thanks Andrea. I'm guessing it was purchased in 2012, and labelled as 'Andrea-2' Filter 52mm'. I can see lots oxidation forming, but still seems to produce usable images.

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How did you attach a lens to it.? Is there an adapter available? Sigma in the UK told me there wasn't one!

 

Lots of sa to m42 adapters on ebay. My tiny El Nikkor looked ridiculous on the sd Quattro body, but it worked fine. Also have a sa to T1 adapter for a vintage lens, that also worked well.

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Gary, about that oxidation. You can remove it before it gets worse using either hydrogen peroxide or cerium oxide.

 

Hydrogen peroxide: Get this from any grocery store or drug store. Soak filter overnight in enough to cover both sides, rinse thoroughly, pat glass dry with microfiber cloth, let dry thoroughly.

 

Cerium oxide: This is glass polish in the form of a paste you can get in various places. (Talk to Cadmium to see if he has any for sale.) It works wonderfully well for removing oxidation. I usually use a microfiber cloth. Sometimes just my fingers. After polishing, rinse thoroughly and pat dry with microfiber cloth, let dry thoroughly.

 

Some folks use purified water for rinsing. I've just used tap water and immediately patted filter dry with the cloth.

 

Periodically removing the oxidation on uncoated filters can keep them going for years.

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Sounds like you have an older Andrea U. Also the reason the Rudbeckia has so much brown in it, might be uncoated, thus oxidation.

Best to remove it from the frame, and use cerium oxide to clean it if it is an uncoated filter version.

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Schott KG1, Hoya HA-50, ~ Kopp 7093.

Thanks for the suggestions, but it appears that the KG1 is almost identical to my CC2 in the IR range. The HA-50 has a very steep slope at 900nm, so likely not as effective. The Kopp 7093 is an odd filter, with sharp slope at 800nm, and cutoff at 900m.

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Gary, about that oxidation. You can remove it before it gets worse using either hydrogen peroxide or cerium oxide.

 

Hydrogen peroxide: Get this from any grocery store or drug store. Soak filter overnight in enough to cover both sides, rinse thoroughly, pat glass dry with microfiber cloth, let dry thoroughly.

 

Cerium oxide: This is glass polish in the form of a paste you can get in various places. (Talk to Cadmium to see if he has any for sale.) It works wonderfully well for removing oxidation. I usually use a microfiber cloth. Sometimes just my fingers. After polishing, rinse thoroughly and pat dry with microfiber cloth, let dry thoroughly.

 

Some folks use purified water for rinsing. I've just used tap water and immediately patted filter dry with the cloth.

 

Periodically removing the oxidation on uncoated filters can keep them going for years.

I've never heard using hydrogen peroxide, but I'll give that a try first. I actually have a small bag of optical grade cerium oxide, to remove some windshield scratches, but never thought of using it on a filter. Thanks for the info!

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Sounds like you have an older Andrea U. Also the reason the Rudbeckia has so much brown in it, might be uncoated, thus oxidation.

Best to remove it from the frame, and use cerium oxide to clean it if it is an uncoated filter version.

It is the older version for sure. Sounds like a good rainy day project. Thanks for the info.

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