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Some thoughts on white balance in UV images and control VIS images

8 replies to this topic

#1 enricosavazzi

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Posted 12 June 2019 - 10:46

New on my site:

http://www.savazzi.n...iteBalance.html
-- Enrico Savazzi

#2 dabateman

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Posted 12 June 2019 - 19:22

Interesting summary.
I think finding a filter combination to get back the look of the stock camera is some what camera specific.
My old full spectrum E510 did well with just a 486 filter, the auto white balance worked. However, this was not the case with my full spectrum converted Em1.
My early best filter for auto white balance was a 4mm BG38 filter.
However, using my same BaaderU custom white balance setting, my 2mm GRB3 filter, equivalent to a KG3 filter provides excellent back to normal colors. This is with sunlight.
Using a white led with low IR, the 486 works on my Em1mk1. So lighting will matter.

Edited by dabateman, 12 June 2019 - 19:24.


#3 nfoto

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Posted 12 June 2019 - 21:35

The BG40 apparently does well on my full-spectrum D600, at least with non-UV specialist lenses attached to the camera. I shoot my Colorchecker Passport and make a dedicated profile in Photo Ninja. Using the Baader UV/IR Cut filter on its own tends to produce a reddish cast that is difficult to get rid of. Haven't tried BG38 + UV/IR Cut yet on that camera -- might be worth a try in conjunction with the UV-Nikkor etc.

#4 Cadmium

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Posted 13 June 2019 - 03:12

I tend to use BG38 alone, usually, it is a little redder than BG40, and BG40 works nice also, and I think BG40 works best for some other cameras than for mine.
I don't stack Baader UV/IR-Cut with the BG38 or BG40, I have tried, and I didn't notice a difference.
I always white balance from RAW(NEF) when shooting a visual shot on my UV/IR cameras anyway.
But 90% of the time I use BG38, then white balance that from RAW.
Some like BG40 better. It tends to look just a little bluer for me, maybe too blue.
S8612 and BG39 are way too blue for me, and Baader UV/IR-Cut looks too red for me.

#5 UlfW

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Posted 13 June 2019 - 04:11

I agree with Steve.
For my camera BG38 give the best results with simple white balancing even if the BG40 is not very different.
Ulf Wilhelmson
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#6 Andy Broomé

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Posted 13 June 2019 - 17:29

I have never stacked any filters for vis - just used my Kolari Vision hot mirror filter (which I guess is the same as BG40) and set a new CWB without issue.

#7 enricosavazzi

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Posted 15 June 2019 - 07:56

View PostCadmium, on 13 June 2019 - 03:12, said:

I don't stack Baader UV/IR-Cut with the BG38 or BG40, I have tried, and I didn't notice a difference.
I don't see a difference either, with ordinary subjects. With my Sony A7 II I do see a difference if the illumination source is particularly NIR-rich (sunlight or incandescent lamps) and the subject is dark in VIS and NIR-reflective (especially some types of black cloth and velvet that I use as VIS-black background).
-- Enrico Savazzi

#8 Mark Jones

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Posted 14 July 2019 - 21:14

Many UV images are only black white and blue in colors. It would be more exciting to use a debayered sensor with a red, green and Venus filter and then use photoshop to make each image the r, g and b (uv) channels
should give some interesting full color/ false color looks.
Peace, Mark Jones, Charlotte, NC, UV amateur photographer.

#9 Andrea B.

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Posted 17 July 2019 - 20:00

You can do that with a typical non-monochrome converted DSLR or mirrorless camera. Shoot the scene under the UV-pass filter and put that into the blue channel. Shoot the scene under the UV/IR-block filter and put that into the red channel and green channel. Or use red-pass and green-pass filters to shoot the red channel and green channel inserts. If you search on the Multispectral tag, you might find some of these stacks.

Multispectral..For uv/vis/ir stacks or for mixed displays.

Also on Ben Lincoln's site you can see multispectral stacking of every imaginable variety. Awesome stuff.
https://www.beneatht...ace_Breaks.html

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Reminder: For accurate visible color from a photo made with Baader UV/IR-cut filter, BG 38, BG 39 or BG 40, be sure to make a color profile for the camera using that filter. White balance alone is not enough to restore accurate colour to a converted camera. Although you can get fairly close with WB alone. :D

.
Andrea G. Blum
Often found hanging out with flowers & bees.