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Sunflower, Canon 40mm, SEU3 + S8612 CWB in camera then PN

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#1 colinbm

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Posted 15 May 2021 - 02:52

Here is my start to processing.......
Sunflower, Canon 40mm, SEU3 + S8612 CWB in camera, open in PN....

PN won't let me click WB ? PTFE not blown & Sunflower too dark ?

Attached Image: 2021 05 15 Sunflower, Canon 40mm, SEU3 + S8612 CWB in camera.jpg

#2 Andy Perrin

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Posted 15 May 2021 - 03:21

The PTFE is blown out as far as white balancing is concerned. If any of the three channels is maxed out then it will not work, but 2 out of 3 would still be unblown then.

Possibly move the PTFE further from the camera and nearer to the flower?

Edited by Andy Perrin, 15 May 2021 - 03:21.


#3 colinbm

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Posted 15 May 2021 - 03:35

View PostAndy Perrin, on 15 May 2021 - 03:21, said:

The PTFE is blown out as far as white balancing is concerned. If any of the three channels is maxed out then it will not work, but 2 out of 3 would still be unblown then.

Possibly move the PTFE further from the camera and nearer to the flower?

Thanks Andy,
I am trying to take good UVA photos & I want to learn this UVA CWB business....
Why is everything OK in the historgram ?
If I move the PTFE closer to the flower I won't be able to crop it out ?

#4 colinbm

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Posted 15 May 2021 - 04:44

Thanks Andy
This time I took the CWB with the PTFE held at an angle to the camera so any reflections were directed down & the the left.
Again I placed the PTFE behind the Sunflower & held at an angle down & to the left to avoid any reflections & I placed the rough sawn face forwards & the saw lines can be seen.....no blown PTFE target.... & a happy Colin
The vignetting of this SEU3 is still obvious :sad:
We'll see how the rest of the simple processing goes....

Attached Image: 2021 05 15 Sunflower, Canon 40mm, SEU3 + S8612 CWB in camera web 2.jpg

#5 Andy Perrin

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Posted 15 May 2021 - 05:01

Yep that works. Don’t forget you can copy and paste the white balance. Take one photo with PTFE and one without and do the white balance on the first one and move it to the second one.

You don’t have the histogram set to show the R, G, and B separately. So you can’t tell if one is saturated but the others aren’t.

Edited by Andy Perrin, 15 May 2021 - 05:02.


#6 colinbm

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Posted 15 May 2021 - 05:20

Thanks Andy
Is this the histogram you suggested ?
Is the blown the high peak on the left ?
I have been looking at the right, to not get too much there ?

Attached Image: 2021 05 15 histogram.jpg

#7 Stefano

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Posted 15 May 2021 - 05:30

Since I too have the "bad habit" to white balance in-camera (but I do use Photo Ninja to boost saturation and have less noise), I wonder if there is a way to select an area instead of a single pixel to white balance from in Photo Ninja. If the image is not too noisy selecting a pixel or the other doesn't make much difference, but an average would be much more accurate. I think a camera does this, it uses the entire image.

#8 Reed F. Curry

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Posted 15 May 2021 - 11:40

Col,
Why are you putting an S8612 over the SEU Gen3? If you want to see if there is an IR leak, just put an R72 over the SEU Gen3 (and also try it with the Gen1 and the BaaderU).
That S8612 is going to crush the UV output of the SEU Gen3, with no positive return.
Just my opinion.
Best regards,
Reed
http://www.uvroptics.com

#9 colinbm

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Posted 15 May 2021 - 11:50

Yeah OK, I was trying to get rid of the vignetting & it was also suggested by Dave to give it a try....
I am waiting for some gear so I can mount filters like this behind the lens......soon

#10 Andy Perrin

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Posted 15 May 2021 - 14:08

Stefano- if you click and drag the white balance tool in PhotoNinja, it will average over the pixels in the path you draw.

White balancing in camera is only bad if your camera doesn’t have the range to set the white balance properly. On my Sony’s there is no difference between PN and in-camera.

#11 Stefano

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Posted 15 May 2021 - 19:24

Thanks. I shoot in .jpg + .CR2, so I have two versions of every image. I am often fine with the .jpgs, but if I want I can play with the RAWs. One thing I should improve is using PTFE instead of a paper tissue for the white balance, but the difference is probably very minor.

#12 Reed F. Curry

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Posted 15 May 2021 - 23:10

Stefano,

I would stick with PTFE rather than white paper. A lot of white paper, especially copier paper, has whiteners added. Usually, TiO2 (titanium dioxide) is used as it is in paints, to absorb UV radiation. TiO2 is florescent (blue) with a UV excitation wavelength; so it does not appear white in the UV. However, the TiO2 treated paper looks brighter in visible light because of the florescence.

Just an fyi.
Best regards,
Reed
http://www.uvroptics.com

#13 Stefano

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Posted 16 May 2021 - 06:28

Yes, this is why I don't use copy paper but tissue paper, it almost doesn't fluoresce. But PTFE is known to have a flat reflectance, so I would stick with it too.

#14 UlfW

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Posted 16 May 2021 - 07:33

I normally matten my PTFE sheets used for WB by scrubbing them with a rather rough grit water sanding paper.
I do that under running water and tries to scrub in all directions, to get a random scratch pattern.
By doing so I decrease the direct specular reflection you normally can get from a PTFE sheet.

This idea I got from how to maintain Spectralon (Fancy PTFE).

Edited by UlfW, 16 May 2021 - 07:34.

Ulf Wilhelmson
Curious and trying to see the invisible.

#15 colinbm

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Posted 16 May 2021 - 07:40

Yes mine have been sandpapered.

#16 Reed F. Curry

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Posted 16 May 2021 - 14:51

I only began to understand how ubiquitous the use of whiteners is when I discovered that TiO2 is added to skim milk. :angry:
Best regards,
Reed
http://www.uvroptics.com