EOS R8: Custom White Balance - Kelvin value?

[justadude]

This is a bit of an off the wall question concerning custom white balance that I'm 99% sure I will not get an answer on, but here goes.  When I set a custom WB and take a photo, is there a way to find a Kelvin value to it in the file?

Let me explain why I am asking...

I am shooting infrared with a full spectrum Canon R8.  When I set a custom white balance I put a 720 nanometer lens filter on the camera, then to set it I make sure the camera is pointing towards green sunlit foliage.  Now if I want to shoot in the 850nm spectrum, I put that filter on, and repeat the custom WB setup steps.  I do this with 5 different wavelength filters each time I change from one to the other.  Sounds like a pain in the... foot.  However after 25 years of doing this it is second nature for my infrared photography.

I've done this with various Kodak, Pentax and Canon cameras over the years.  Never had a problem with getting a nice custom WB... until the R8.  I can nail 4 of the 5 wavelengths each time I set a custom WB, with the exception of the 720nm.  I have no idea why this one is hit or miss on this particular camera, and only at this wavelength, but never on any other wavelength or other camera (including any of my other Canon cameras).

So my thoughts are IF there is a way to determine a Kelvin value of a file (or any other way to tell the temperature that I'm not thinking of), maybe on the rare times that I hit the correct custom value, I could look it up, then set Kelvin values from that point on.

Also, to my knowledge, if I save settings as a Custom Program setting on the menu, it won't keep the WB in the Custom menu once I change the custom WB for a different wavelength.  At least that was my experience with other cameras.

[justadude]

"You are correct that it is more complicated than a single Kelvin number.

Exiftool will calculate RedBalance and BlueBalance from the WB_RGGBLevels associated with the chosen white balance. I have not looked at how the calculation is done. If one selects "Daylight" WB, then it appears to be that the Kelvin value will always be 5200. If one selects "Auto WB" then it appears to me that the reported Kelvin value is not meaningful."


I pretty much thought it was more than just a Kelvin number

[justadude]

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@Waddizzle wrote:

I usually shoot RAW and dial in a color temperature when shooting in sunlight. I use Auto WB White Priority under artificial lighting. 

I use Adobe LR, but I am on my phone with no access to it until later tonight. But I believe that you can adjust the color temperature and tint using sliders, provided that you shoot RAW. 

I shoot RAW as well, but set the WB depending on which wavelength I am shooting.  It varies considerably.  Yes, you can adjust the sliders in LR - I've been using LR for infrared since the first beta version came out in 2006.  But something is missing with the R8 and 720nm that I hit sometimes, and miss more often.  It's the blues in the skies that you normally see well at 720nm, but a lot of the images lack the blue.  If I shoot 590nm I can still get just as much blues as I have with any other camera.  Same with 665nm.  

I know infrared light is invisible to the human eye... but after 40ish years of being heavily into infrared I can actually read what the infrared light should be fairly well.  It's not just amount of sunlight vs. amount of clouds, or the direction of the sun compared to direction you are shooting... how close the sun is to the horizon plays a bigger part than it does in visible light photography.  Also, how close you are to large bodies of water (not being right next to them, but if I am within a mile of one of the Great Lakes, the IR light is going to bounce of the sky more).  So images that should produce strong blues do not at 720nm as often as they should - and sometimes I need to reset the Custom WB a handful of times before it works... and it will continue to work... until I decide to shoot a different wavelength, change the custom WB, then the next time I go back to 720nm I play the game of hit or miss again.  This is the only wavelength that is this finicky, and only on this camera.

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[justadude]

I will play around with the 2D adjustments in DPP4, but only to see what happens one time.  I have a 2024 iMac M4 with 32GB memory, and DPP runs as slow as it did on my 2019 iMac.  I actually have to wait on average a minute or more every time I move a single slider in order to see the change.  It is horribly sluggish.  Yes, everything is up to date as far as software and iOS, no the hard drives are not even close to full, and every other program I use is lightning fast.  So this will be interesting to see what happens with those adjustments compared to Photoshop and Lightroom, but I don't want this to be a regular workflow solution.  And in all honesty, I think the problem lies in camera because I've always been able to pull correct colors out of infrared files since digital infrared first became a thing, but in some of these 720nm files on the R8 the colors are just not there depending on what the custom WB was when they were shot... and again, only in the 720nm range.