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UltravioletPhotography

[Filter Test] Shots of Nichia 365nm Torch


Andrea B.

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I had to try this.

Conclusions may be drawn by the interested reader.

 

Kindly Note: I like and use all the 4 filters in this test. I'm not out to show up one against the other. I consider each filter well made and good for general UV photography. I was simply curious as to what such a test might show.

 

Gear:

  • Nichia 365nm UV-Led Flashlight on Low Power
    • It is hard to stare down the barrel of a Nichia 365nm UV-Led torch without serious blowout. I used the lowest power setting on my torch, but even then it was tricky. So I turned the torch a bit to the side. If that is not a valid idea, let me know. I'm wingin' it here!

    [*]UV-Nikkor 105/4.5

    • All shots made at f/11.

    [*]D610-broadband

    • ISO-400.
    • Monochrome[0] picture control. I didn't want colour to obscure the result.

    [*]In total darkness, so no ambient UV.

    • WEARIN' ME LI'L' GOGGLETS, YEAH. U must do this or else...!!

    [*]The initial spot-metered reading for all 4 filters in Live View was the same at 2.5".

    • I ran a series of 4 more faster stops over that.
    • Metering is tricky when staring down the barrel of a UV-Led torch,
      but we have to start somewhere.

.

Filters in alphabetical order

  • BaaderU
    • 350FWHM60 [320-380nm]
    • 85% trans rate at peak

    [*]KolariU

    • 365FWHM40 [340-380 on website, but 345-85?]
    • 50% trans rate at peak

    [*]StraightEdgeU

    • 379FWHM43? [342-385nm, peak shifted right within that range]
    • 85% trans rate at peak

    [*]U-360 (2mm) + S8612 (2mm)

    • 365FWHM60 [325-385nm estimated from charts]
    • 60% trans rate at peak
      (You could use a 1.5mm thick S8612 and raise that trans rate. I'm in the land of overkill using a 2mm thick S8612.)

  • The two highest transmitting filters at peak are the BaaderU (85% @ 350nm) and the StraightEdgeU (85% @ 379nm). But the UV-Led has a peak at 365nm. We therefore conclude .

  • The lowest transmitting filters at peak are the KolariU (50% @ 365nm) and the U-360 stack (60% @ 360nm). These two filters best match the UV-Led peak at 365nm. We therefore conclude .

The individual photos were center-cropped, labeled, resized and converted to TIFs in Photo Mechanic.

The composite was constructed in PSE 11. No other edits were applied.

This composite is 1500 x 1200 pixels if clicked up.

torchtest.jpg

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I didn't see any difference either.

This test was an attempt to mimic the similar test on Kolari Vision's blog.

https://kolarivision...uv-filter-test/

 

That test was made with a lens which does not transmit UV as well as would a dedicated UV lens. Upon seeing that test, I immediately wondered what would happen if I used the UV-Nikkor to shoot down the barrel of a UV-Led flashlight. Then went and did it.

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