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UltravioletPhotography

[Filter Test] Hoya U340 x 4.00 mm [Added: Good Test Flower, Also]


Andrea B.

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Added: The flower in this test was from the grocery store. It is some type of chrysanthemum. As it turned out, the red and yellow patterning in the flower carried over to its UV appearance. Thus it makes for a very nice test flower for UV work. I don't know whether this type flower is available during the winter months in the Northern Hemisphere, but look for them if you need a UV test subject with "known" response. Sunflowers, another good UV test subject, are often available now year round from a florist or grocery in the US.

 

Equipment: D600-broadband + Coastal Optics 60/4.0 + Sunlight

 

From left to right along the S shape:

  • Visible using Baader UVIR-Cut
  • Unfiltered (a Visible and IR mix)
  • B+W 092 IR-Pass (IR with a bit of high Red)
  • U-340 (4.00mm) only (UV with Red/IR)
  • U-340 (4.00mm) + U-340 (1.00mm) only (almost all UV)
    At 5.00mm of thickness, the U-340 glass suppresses quite a lot of the Red/IR. The flower's UV-signature is obvious with only a small amount of fade. Increasing contrast slightly in the editor would remove the fade.
  • U-340 (4.00mm) + S8612 (1.75mm) UV-Pass Filter Stack
  • U-340 (4.00mm) + U-340 (1.00mm) + S8612 (1.75mm) UV-Pass Filter Stack
  • StraightEdgeU UV-Pass
  • Baader UV-Pass

I'd like to repeat this experiment using various thicknesses of IR-blocking glass to determine an optimal filter stack for U-340 filter glass. I think the 1.75mm thick S8612 filter I used this time for IR-blocking was fairly strong. Maybe I'd shorten the exposure time a bit if a 1.00mm thick S8612 filter worked just as well?

 

Photo will click up to 1200 pix width in expanded browser.

Conversions made in Photo Ninja. Composite made in Photoshop Elements 11.

composite_20161016wf_9flowers.jpg

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Thanks for the charts, Steve!!!

Did you like my presentation? :D :D :D

 

I had a great time playing with the U-340 glass!!! I agree the 1.75 IR-blocker is a bit strong. And I don't like that it pushes the peak to the right (although not by much). I want to stay around 340nm. So the graph of the 340 in 6mm thickness looks good.

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Yes, nice presentation. :-)

The difference looks like about 7nm to 8nm, which is not exactly a small difference in the peak wavelength. You simply don't need that much suppression.

OD5 is more than enough, and it gives you more UV amplitude (about 15% more), and lower peak wavelength of about 343nm (your OD7 is more like 350nm peak).

Also, I would try with the UV-Nikor, you might get more cerulean/turquoise with the thick non-suppressed U-340 only filter/stack. Just a guess.

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