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Author Topic: White balance as per-channel exposure correction  (Read 2690 times)

Iliah

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White balance as per-channel exposure correction
« on: November 23, 2017, 03:33:24 pm »

This article tries to explain some of the inner workings of white balance
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digitaldog

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Re: White balance as per-channel exposure correction
« Reply #1 on: November 23, 2017, 04:12:52 pm »

Another winner/keeper. Good and important point for readers that only 'well behaved' (RGB working spaces) are neutral when RGB values are the same. And this is something we keep having to repeat for some reason but short, sweet and to the point:


As you can see, changing the white balance setting in the camera doesn't affect the underlaying RAW data in any way. The histograms are the same, and adjusting the white balance to the same value on all of the shots results in the same look and color.
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Tim Lookingbill

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Re: White balance as per-channel exposure correction
« Reply #2 on: November 23, 2017, 05:13:47 pm »

Found this article linked to at the bottom of the OP linked FRV site on calibrating a camera's exposure for Raw capture quite informative...

https://www.rawdigger.com/howtouse/calibrate-exposure-meter-to-improve-dynamic-range

From the quality of the previews generated in the screenshots of the apps I wonder if there's a way to get Rawdigger or FRV to just convert to tiff. I wonder what they use under the hood to get those lovely previews that seem to have very natural color and tonality as opposed to the ashen and dark previews I get from Adobe's defaults.

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digitaldog

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Re: White balance as per-channel exposure correction
« Reply #3 on: November 23, 2017, 06:22:49 pm »

From the quality of the previews generated in the screenshots of the apps I wonder if there's a way to get Rawdigger or FRV to just convert to tiff.
You want RD to export a TIFF? Did you examine this menu item:

Quote
I wonder what they use under the hood to get those lovely previews that seem to have very natural color and tonality as opposed to the ashen and dark previews I get from Adobe's defaults.
Start by asking Iliah.
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Tim Lookingbill

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Re: White balance as per-channel exposure correction
« Reply #4 on: November 23, 2017, 06:26:38 pm »

I missed that from glancing through the site and reading the articles. There's a lot to read including the feature list of each app. Export On Tiff didn't jump out at me.

Thanks, Andrew, for the head up.
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Tim Lookingbill

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Re: White balance as per-channel exposure correction
« Reply #5 on: November 23, 2017, 07:17:30 pm »

Gave FRV a try.

It's certainly fast and it really shows I have a terrible, crappy lens and noise ridden camera and that I should just throw them all in the dumpster and give up photography.

I think I'll just stick with CS5 ACR. Compared to what I just experienced just now I'll stay in my fantasy world and REALLY appreciate Adobe Raw Converter.

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digitaldog

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Re: White balance as per-channel exposure correction
« Reply #6 on: November 23, 2017, 07:20:01 pm »

It is so fast, it illustrates what an utter performance slog Lightroom is with respect to previewing in Grid etc.
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Tim Lookingbill

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Re: White balance as per-channel exposure correction
« Reply #7 on: November 23, 2017, 07:44:13 pm »

I'm assuming you're referring to the slow thumbnail preview generation in the latest version of LR.

I have slowness in LR4 but only after applying a series of tweaks with the sliders where the main preview does a blurry screen for a couple of seconds and then the updated edits. Library modul in film strip mode doesn't continually refresh the previews.

But not so in Bridge where thumbnail generation is slow on folders of images I haven't looked at in some time. I've got 8GB of Ram and it takes about 3 seconds for each image to show the xmp edits I've applied months ago to a folder of 20-40 6MP PEF's. I have "Browse Quickly By Preferring Embedded Images" selected. If that is turned off the little wheel of thumbnail updating will spin for what seems an eternity and slow the launch into ACR.

Click on a recently worked folder of Raws and it's about 1 second per image.
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Iliah

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Re: White balance as per-channel exposure correction
« Reply #8 on: November 23, 2017, 08:42:00 pm »

it really shows I have a terrible, crappy lens and noise ridden camera

You can press "J" to see the embedded JPEG.

In FastRawViewer we do not perform full high quality demosaicking, as we don't see the need in that for selecting what images to keep.
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Iliah

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Re: White balance as per-channel exposure correction
« Reply #9 on: November 23, 2017, 08:45:27 pm »

Another winner/keeper. Good and important point for readers that only 'well behaved' (RGB working spaces) are neutral when RGB values are the same. And this is something we keep having to repeat for some reason but short, sweet and to the point:


As you can see, changing the white balance setting in the camera doesn't affect the underlaying RAW data in any way. The histograms are the same, and adjusting the white balance to the same value on all of the shots results in the same look and color.
Thank you. Of course the article covers very limited ground, in the next one we plan to add some more details, like showing how "colour of light" affects noise because of the underexposure of the red/blue channel (for warm / fluorescent light)
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digitaldog

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Re: White balance as per-channel exposure correction
« Reply #10 on: November 23, 2017, 10:09:03 pm »

Thank you. Of course the article covers very limited ground, in the next one we plan to add some more details, like showing how "colour of light" affects noise because of the underexposure of the red/blue channel (for warm / fluorescent light)
Great, after which this fellow might need to check it out:
http://forum.luminous-landscape.com/index.php?topic=121761.msg1012847#msg1012847
Appears a caviller attitude towards exposure is just fine all that's necessary these days. For some....
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Iliah

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Re: White balance as per-channel exposure correction
« Reply #11 on: November 23, 2017, 10:25:28 pm »

Great, after which this fellow might need to check it out:
http://forum.luminous-landscape.com/index.php?topic=121761.msg1012847#msg1012847
Appears a caviller attitude towards exposure is just fine all that's necessary these days. For some....
It is hard to understand what the problem with proper exposure is.

Going by JPEG, one may underexpose raw by more than 2 stops. This JPEG has blown-out red channel:


Raw is 2+ stops underexposed:
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