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UltravioletPhotography

[Filter Test] 340/10 #1 Gotta work out a problem or two, but here is a 340/10 result anyway


Andrea B.

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[Filter Test 340/10 #2] Cured the flare but it's ring around the posy here

[Filter Test 340/10 #3] Trying again with the 340/10

[Filter Test 340/10 #4] Edmund Hard-coated 340/10 Rear-mount Experiment

[Filter Test 340/10 #5] Edmund Hard-coated 340/10, Sunflower, Sun

[Filter Test] 340/10 #6 Progress was made, finally. UPDATE: Progress was then lost.


 

 

 

While out testing one of the new UV-Pass filters yesterday, I decided to try the 10 nm narrowband 340 UV-pass I was so eager to get. Let's just say I have a couple of details to work out about how to properly use this one!! It is very hard-coated and extremely shiny (mirrored!) on both sides. So guess what happens? Yes, flare. Lots of flare. BTW, this was not unexpected on my part, but it does not always occur. I'll probably need to keep a lens hood handy.

 

The 340/10 false colour response is primarily in the red and green channels. Quite interesting. See raw versions below.

 

More experiments to come as I get time.

 

 

Here is the test subject visibly rendered: The so-called Evil Clown of Middletown, NJ -

once a rotating sign for the Food Circus grocery store -

and the subject of much hilarity amongst the township's teenage population -

and popping up in the occasional movie or two (Clerks II).

The photo clicks up to 1000 pixels wide in an expanded browser.

clown_visSun_20160820middletownNJ_49166pn.jpg

 

 

And here is the result from the 340/10 with white balance on the clown's nose.

Kindly note without comment that I'm showing you this photo with all its flaws on purpose

so that you can learn - in case you didn't already know -

that UV photography is always fraught with Things That Easily Go Wrong:

flare, dark shadows, oil splashes from wonky camera shutters and so on.

Yes, this sensor cover was pristine at 14.34.48 when I made the visible version

and by 14.53.50 it was a total mess.

The photo clicks up to 1000 pixels wide in an expanded browser.

clown_uv340FWHM10Sun_20160820middletownNJ_49258pn01.jpg

 

 

A crop from the raw version from Raw Digger.

Remember RD says this is properly exposed. Hmmmm......

clown_uv340FWHM10Sun_20160820middletownNJ_49258raw.jpg

 

A crop from raw red channel.

clown_uv340FWHM10Sun_20160820middletownNJ_49258rawRed.jpg

 

A crop from raw green channel.

clown_uv340FWHM10Sun_20160820middletownNJ_49258rawGreen.jpg

 

A crop from raw blue channel. Almost nothing.

clown_uv340FWHM10Sun_20160820middletownNJ_49258rawBlue.jpg

 

The Raw Digger histogram.

Note that there is only a 3 EV range here.

Can you see from this why the bright areas are orange?

clown_uv340FWHM10Sun_20160820middletownNJ_49258histo.jpg

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I don't know for sure.

The hard-coat is applied as a single-coat plasma deposition. So I'm not sure if lack of the usual layers would make a difference? However given that such a filter reflects unwanted wavelengths rather than absorbs them, the angle of incidence could still cause dichroic effects?

 

Dichroic effects show up in rings mostly. I think I see a bit of that in the UV photo moving from center to edge - in the form of colour rings maybe. The washed out areas are much more flare like than anything else.

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You really really need to clean that sensor :D

 

Not surprised that you got loads of reflections and other artefacts. Shiny filters and digital sensors don't go too well together. The longest possible lens shade is always a must, after having scrutinised the setup for possible light leaks. Sometimes rear-mounting the filter helps too.

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I did clean the sensor cover. As mentioned, it was pristine when I started the shoot. It is the oil slinging shutter which makes this mess after just a few shots. You'd think that by now all the oil would have been slung already.
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Andrea, do you have had the shutter unit of that D600 replaced?

Bjørn, no. The warranty was voided when I had the full spectrum conversion made. So I have not tried to send it in for shutter replacement. Now that I am back home, it is time for me to get busy with acquiring an upgraded full spectrum camera - either the D610 or a D750. I don't think I want to convert a D810.

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Hm. Apparently warranties work differently in various parts of the world. Nikon Nordic has replaced the shutter unit on my D600 twice - first time, I asked, the last time, the camera was in for normal maintenance and check-up and the techs decided to put a new shutter unit into it.
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I suppose I could try to have it fixed. But I'm ready for a Nikon full-spec upgrade. :lol:

The Sony a7R was just too hard to work with.

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... it is time for me to get busy with acquiring an upgraded full spectrum camera ...

... The Sony a7R was just too hard to work with.

 

I was about to ask what about your recent A7?

I thought the images you posted with it were superb. But then so are your Nikon images.

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The Sonys are made by engineers without any knowledge of photography or how cameras are used in the field. I just sold off my A7, couldn't bear using it any more.
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I just sold off my A7, couldn't bear using it any more.

 

Did you really!!!! Oh my. OTOH, you have used Nikons for so many years that the frustrations provided by the a7 probably just are not worth tolerating. Thing is, I never felt those frustrations with my nifty little Lumix GH1 like I have with the Sony. The only problem with the Lumix GH1 was the image quality for UV can be problematic because it is always difficult to have enough UV illumination. I rely a lot on the newer Nikons with their lower noise at higher ISOs - so useful in UV documentary work.

 

I was about to ask what about your recent A7?

 

I thought the images you posted with it were superb. But then so are your Nikon images.

Well, thank you (blush!).

I have indeed gotten some good images with the a7R. But not easily. Some cameras get in your way. Some do not. But we will see..... I don't think I am done with the a7R just yet. One thing which I did not think through fully was that the a7R shoots a kind of compressed raw which - as it turns out - does not lend itself well to UV imagery. So I am occasionally seeing some artifacts which I would not typically see in UV work using the Nikons 14-bit raw.

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It looks like a light leak, but it could be the filter. Is this an Edmund's or Omega/eBay filter?

Do you get the same anomaly pattern if you shoot different scenes without rotation or changing the filter/lens/camera?

Try rotating the filter a bit ans see if the anomaly moves.

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As mentioned, this flare thing does not always occur. I'll get some proof of that us soon.

 

This is the Edmund hard-coated 340FWHM10 filter.

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I just now noticed the black spots, are those part of the problem, or a separate issue like a dirty sensor?

When you have the other main problem that looks like a light leak, is it always in the same area of the photo?

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