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Second test with Sigma Quattro camera for UVR

UV Camera
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#1 Adrian

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Posted 17 October 2018 - 15:03

A second test with the Sigma Quattro sd camera. This is a carnivorous pitcher plant: Nepenthes reinwardtiana. This fascinating species is unique in having invisible spots inside the pitcher, which UVR reveals. Most specimens have two spots, but some have three, and this one has one. No one knows their function!
Technical specs:
Sigma Quattro sd camera with "dust protector" filter remover. El Nikkor 105mm lens. 1/160th second @ f/22 at 200ISO (this same subject, on my full spectrum Nikon D300 with same lighting etc would need f/8 at 400ISO!). 2 x "full spectrum" Metz 45CL1 flash guns. I have not attempted to white balance the images. The visible light control was shot with a Kolari Hot Mirror filter over the lens.

Attached Images

  • Attached Image: N. reinwardtiana sigma lo res.jpg

Adrian Davies
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#2 dabateman

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Posted 18 October 2018 - 07:16

I think its hard to compare cameras by memory and best to directly compare them at the time. Especially with changing sunlight. When I compared my SD14 to my Spencer converted E510, I found the SD14 to be 1 to 2 stops faster than the E510. Both were limited to about 340nm.

I just compared the SD14 to my EM1 full spectrum converted camera by Kolari Vision. They have very similar exposures using 390bp25 and 370bp15 filters, the EM1 may be faster at 370, though. The EM1 jumps miles ahead with 340bp10, 335bp10 filters. A 2 minute ISO 200 f8 image using 335bp10 filter on SD14 was dark. Whereas a 30 second ISO200 f8 image with the EM1 was correctly exposed. This was using the same UAT 85mm f4.5 lens on each camera and a 160W Lucky herb mercury vapor lamp.

I look forward to testing the new Quattro, But I have my doubts. From what I read the sensor may be less sensitive to UV. But I will only know after I test it.

What the SD14 has really shown me is the quality of conversion. The EM1 is really amazing sensitive camera and I am glad I had Kolari Vision convert it.

All that aside I do like your image above. The cup is really pounding out with intensity.

#3 Andrea B.

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Posted 18 October 2018 - 14:59

Adrian, in Photo Ninja the white balance dropper can be applied to a JPG or TIF with fairly good results. Here is what I got when I white balanced the UV portion of the posted photo in PN. The dropper was applied to the magenta area inside the Nepenthes. I then moved the saturation slider for the magenta patch all the way left to eliminate a very small remaining tinge of magenta.

What I notice in this UV photo is that there seems to be some loss of textural detail along the pitcher? Is that a focus issue? Or simply the way the photo came out? Just curious.

Attached Image: post-47-0-17985400-1539788451pn.jpg
Andrea G. Blum
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#4 Andy Perrin

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Posted 18 October 2018 - 15:04

Andrea, it looks like the front is out of focus to me. See how the lid of the pitcher is blurry at the tip and sharp in back?

#5 Andrea B.

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Posted 18 October 2018 - 16:01

I've had this kind of thing happen because what appears to be a stationary plant or flower in the indoor studio still can behave organically and might wilt or occasionally move itself in response to the UV light. It can be disconcerting because you think you have set things up properly, get some motion blur or OOF shots, and then wonder what-the-heck just went wrong. :D :D :D
Andrea G. Blum
Often found hanging out with flowers & bees.

#6 Andy Perrin

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Posted 18 October 2018 - 16:09

I imagine that is especially true of carnivores since they have to move to eat.

#7 GaryR

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Posted 18 October 2018 - 18:37

Adrian,
When I had the sdQ, I was never able to get satisfactory color UV images, on par with a Bayer-sensor digital. I found the foveon sensor to be very selective, in regards to UV and IR sensitivity. Virtually all of the UV sensitivity is in the blue layer, which means you'll have to shoot in monochrome mode for the best results. I selected Monochrome mode, then set the 'Filtering Effect' slider to 'B'. The 'G' green layer has slight UV sensitively (unusable), and the 'R' red layer has zero.