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UltravioletPhotography

[Filter Test] 293BP10: It's Rough Down There Below 300 nm


Andrea B.

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I've said before and I'll say it again: I really can't shoot anything around 300nm.

Here's more proof.

 

Equipment: GH1-broadband + Asahi 85/4.5 Ultra-Achromatic-Takumar + 293BP10 UV-Pass Filter

Shot outdoors in strong sunlight, although it is still March so UV could be low.

 

I shot two sets of three - one set with shiny side of a 293BP10 filter facing in and one set with the shiny side facing out - just to be sure there wasn't any effect from filter orientation.

Both sets were shot at: f/4.5 for 15" @ ISO-1600 with EV=+3.0. (I forgot to put the EV boost on the foto labels.)

 

In each set's sequence of three, the edits in Photo Ninja were as follows:

  • Demosaic only - to try to show just the raw capture
  • Demosaic with brightening curve ("gamma") applied.
    Brightening the photo only served to bring out the awful noise.
  • Demosaic and curve with GH1 colour profile applied.
    This really did not change anything, but seemed to improve the noise a bit. Go figure.
  • No attempt at white balancing was made.

Recall that the Ultra-Achromatic-Takumar has been designed to be apchromatic between 220nm-1000nm. So there's no problem passing what little UV there is down around 300nm to the GH1 sensor. The results are massively noisy. The Labsphere standards (at left) are incredibly useful in this range. The CC Passport (at right) pretty much disappears. Not that we really need to use the CCP for UV work, but it's a tradition to include it I guess. In the bottom middle of the photo is the filter box for the 293BP10 so's that I would easily recognize what I had been testing when it came time to name the files.

 

Domments and suggestions are always welcomed! I have no fish to fry here, and I might have done something wrong. Let me know!

 

SET 1: Shiny side of filter facing the subject.

Demosaic only.

GH1_UAT85_293BP10OnlyDarkSideIn_Sun_wbManual_20150312wf_125914pn_demOnly.jpg

Demosaic + GH1 brightening curve.

GH1_UAT85_293BP10OnlyDarkSideIn_Sun_wbManual_20150312wf_125914pn_demGam.jpg

Demosaic + GH1 brightning curve + GH1 colour profile.

GH1_UAT85_293BP10OnlyDarkSideIn_Sun_wbManual_20150312wf_125914pn_demGamProf.jpg

 

 

SET 2: Shiny side of filter facing the sensor.

Demosaic only.

GH1_UAT85_293BP10OnlyShinySideIn_Sun_wbManual_20150312wf_130009pn_demOnly.jpg

Demosaic + GH1 brightening curve.

GH1_UAT85_293BP10OnlyShinySideIn_Sun_wbManual_20150312wf_130009pn_demGam.jpg

Demosaic + GH1 brightning curve + GH1 colour profile.

GH1_UAT85_293BP10OnlyShinySideIn_Sun_wbManual_20150312wf_130009pn_demGamProf.jpg

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Wouldn't that be so cool !!!!

Although I'm not sure what I would photograph with a corona cam. :(

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Hooray !!!

 

I see that I and my Nikon D7100 is not the only combination that get's BANDING :(

 

Bet you didn't know that's what you were going to show.

 

It now seems to me that almost any sensor will show it if you push hard enough. Topaz Denoise has a good debanding option which seems to work (probably by scrambling the noise to get rid of the lines so you can't see them as clearly in the dark areas).

 

Dave

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Bill De Jager

Wouldn't that be so cool !!!!

Although I'm not sure what I would photograph with a corona cam. :unsure:

 

UV emissions from power lines. I gather that's the kind of corona they're talking about.

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  • 8 months later...
I never discussed possible visible light leak back when I first posted this test. I don't think there was much visible light leak because I would have seen more of the CC Passport in the shot? But I cannot be sure, of course.
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