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Author Topic: Xrite DNG Profile and white balance  (Read 4088 times)

Charles Beasley

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Xrite DNG Profile and white balance
« on: October 23, 2015, 01:16:05 am »

FWIW, I did search here and dug through the results for about an hour and didn't find this exact question asked. So if it has been, please forgive me.

After a long, long time with Capture One, I have moved to Lightroom. I am working now to build a single illuminant DNG profile for my Canon 5D for studio use only with the XRite software following the procedure set forth by Lee Varis in his book Skin. I am using a PCB Einstein in a Larson 4x6 softbox as the only light source. My camera room is completely covered with black fabric. I have a large (8.5" x 11") sheet of the lightest gray (Neutral 8-the lightest gray patch-next to white) material purchased from XRite that I use to do a custom white balance on a raw file, and then light a standard Colorchecker as evenly as possible. I make a series of bracketed raw exposures in 1/3 stop increments. Since I did the CWB on the Neutral 8 sheet, my colorchecker raw files are within .1 RGB values in Lightroom of being perfectly neutral for the neutral 8 patch. As per Lee Varis, I set the Camera Calibration to Camera Neutral and select the file that has a Lightroom value closest to 50 for the Neutral 5 patch to build the profile. I apply no sharpening, no curve, no white balance, no nothin' before building the dng profile.

When applied to headshots, the images look better than Adobe Standard or Camera Standard (I pretty much like the look of the Camera Standard jpegs, but shoot raw,) but seem too saturated, so I start reading up and have played around with the DNG Profile editor a bit and will continue with that.

But while doing this, I had a shocking discovery. When I apply the profile to the perfectly neutral  custom white balanced raw file of the color checker that I used to build the profile,
I find that it is now no longer neutral! A bit of googling took me to this Xrite blog post:
http://blog.xritephoto.com/2013/11/questions-using-x-rite-colorchecker-passport-lightroom/#sthash.B2B51Eum.8IrdbF96.dpbs
that makes it sound like they think it is perfectly expected behaviour to have to re-white balance files after the profile is applied.

I have my camera room so standardized that I shoot a CWB at the beginning of each session and don't really think I should have to do another "click-balance" in the raw converter.

Is this the way it is supposed to work? Doesn't seem right to me.

TIA,

Charles Beasley
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torger

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Re: Xrite DNG Profile and white balance
« Reply #1 on: October 23, 2015, 03:21:08 am »

I haven't read the full xrite post (it's too long for me:) ), but I suspect this is the Adobe white balance shift quirk:
http://www.ludd.ltu.se/~torger/photography/camera-profiling.html#white_balance_shift

You're right it's not a good behavior, but it's not XRite's fault, it's Adobe's. Due to their design the only way to not cause a white balance shift is to copy the color matrices from Adobe's bundled profiles. If you're a bit of a hacker you can do that yourself, using dcpTool or my own DCamProf. The color matrices are only used for white balance temperature estimations so even if copied you will have the color from the new profile.

If they had stored white balance multipliers instead of color+temp (like they do for "as shot") it would have worked, and I see no sane reason to do the way they have done it now, but now when it is the way it is it's hard for them to change as it would break backwards compatibility. In any case it's unfortunate for us third-party software makers.
« Last Edit: October 23, 2015, 03:24:19 am by torger »
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Charles Beasley

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Re: Xrite DNG Profile and white balance
« Reply #2 on: October 23, 2015, 04:26:58 am »

Torger-thanks for the quick reply. I'm not a hacker or even a command-liner, or I would have already been trying your product! In the link you so generously supplied I am confused by this:

>>>"This means that if you open a raw where you have set a custom white balance and then change profile to your new one you will get white balance shift. This had not happened if Lightroom had stored the white balance multipliers itself, which it does if the white balance is kept at "as shot". "<<<

EDIT: I went back and reset the raw file, which had been shot with a CWB in camera, to "as shot" and rebuilt the profile from within LR, exited LR, reluanched and applied the new profile to the colorchecker file the profile was made from, and two things changed:
1) It still says "as shot" but the temp and tint numbers changed
2) However, this time the gray patches in the Colorchecker are still neutral.

So, Couple other questions if you have the time-

1)would it make a difference if I export a dng and make the profile outside of LR?

2)would it make a difference if instead of a CWB I set a Kelvin temp in camera instead? [the Einstein itself is perfectly neutral 5600K (as set in the camera-not sure what LR numbers would be) and in the softbox I'm using it R=B and G is 1 or 2 pts higher at 5300K] using the Xrite light gray target.
Then leave the file "as shot" either exporting the profile from within LR or exporting the dng and building the profile outside?

TIA
CB

« Last Edit: October 23, 2015, 05:40:45 am by Charles Beasley »
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torger

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Re: Xrite DNG Profile and white balance
« Reply #3 on: October 23, 2015, 06:18:13 am »

It works like this:

The DNG profile contains "color matrices", these are not used for actual color rendition (the forward matrices are used for that) but as a way to estimate what a specific combination of raw red + blue + green means in terms of light temperature and tint. When you make a new profile, using X-Rite's software, my software or anyone elses, they will calculate their own color matrices. The problem is that having just three raw channels (RGB) is totally inadequate when it comes to calculating a light temperature, and on top of that there's no standardized definition of light temperature + tint. This means that different software will make different color matrices, even if shot under the exact same conditions, and it will result in different temperature+tint combinations. In the daylight range (5000K - 6500K) it's not uncommon that two profiles can differ up to 500K in their estimates.

This would not have been a problem if Lightroom just presented temp/tint as a "fun fact" and handles for sliders. However, as soon as you change to a custom white balance Lightroom will store the temp and tint as your white balance setting. It does not care about the actual RGB multipliers that is applied on the raw data. When you load a file it will thus check temp+tint, run that through the profiles color matrices to get the RGB multipliers and those are then applied.

That is if you change profile to one with different color matrices than the previous profile, the resulting RGB multipliers will be different and thus you get a new white balance.

"As shot" is an exception. In this case Lightroom will take the RGB multipliers directly so the tint won't change when you change profile, but instead the temp/tint combination change as it then calculates it the other way around: it takes the RGB multipliers and feed it to the profile color matrices to get a temp tint estimation.

Temp/tint is a very bad unit for white balance if you want something well-defined and stable. But it's something that is more intuitive than three RGB numbers to us photographers. The least bad solution would be to always store RGB multpliers but show temp/tint in the GUI and let the temp/tint jump around a bit when you change profile, that is always run it like in the As Shot mode. But that's not how they do it.

So to the questions;

1) no it won't make a difference if you export a DNG and make the profile elsewhere. The only way to not have this effect is to copy the color matrices from the original profile.
2) On the raw level white balance is always RGB multipliers (unless you have some exotic camera with other channels than RGB), but as a user you never get to see those directly. Different manufacturers have different ways to translate those into more user-friendly numbers, usually a temperature+tint combination. However as said there is no standard how this is done, and even if it was the three RGB channels are too few to make an accurate conversion. That is your camera's understanding of what 5300K is is probably a quite bit away from what Lightroom's standard profile 5300K is. But anway, say you set a custom white balance in your camera that makes your patch perfectly neutral this means that you can leave the WB in Lightroom at "As Shot", and then you can switch profiles without getting a shift. So yes in that case it makes a difference.

What kind of Canon 5D do you have? 5D mk III, 5Ds? 5DII, original 5D?
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sTi

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Re: Xrite DNG Profile and white balance
« Reply #4 on: October 23, 2015, 07:24:17 am »

Is this white balance shift specific to Lightroom or is it also necessary to pay attention to this in other software that can make use of DCP profiles like Raw Therapee?
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torger

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Re: Xrite DNG Profile and white balance
« Reply #5 on: October 23, 2015, 07:29:55 am »

Is this white balance shift specific to Lightroom or is it also necessary to pay attention to this in other software that can make use of DCP profiles like Raw Therapee?

There may be other raw converters that behave like Lightroom, I haven't tried them all. RawTherapee does not behave this way though. RawTherapee has built-in color matrices and always use them for the white balance sliders, the color matrices in the DNG profiles are simply ignored.

(More accurately put: they're used for a DNG-profile-local white balance that's not visible to the user, that local white balance is used as a guide to mix forward matrices in dual-illuminant profiles, so yes color matrices can have a small effect on color, but that's a very minor effect and just complicates this discussion)
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digitaldog

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Re: Xrite DNG Profile and white balance
« Reply #6 on: October 23, 2015, 10:35:56 am »

But while doing this, I had a shocking discovery. When I apply the profile to the perfectly neutral  custom white balanced raw file of the color checker that I used to build the profile,
I find that it is now no longer neutral!
Re-white balance. DNG camera profiles and WB are separate by design.
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Andrew Rodney
Author “Color Management for Photographers"

Charles Beasley

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Re: Xrite DNG Profile and white balance
« Reply #7 on: October 23, 2015, 06:31:51 pm »

Torger-FWIW-I reshot new targets, one with a K white balance (lightest gray R-G-B=78.4-78.6-78.5) and one with a CWB closer to neutral ( R-G-B=78.6-78.5-78.6.)
I exported both to profiles leaving LR "as shot" and the results both work the same way. When I apply the profile, LR still says "as shot," but the K value and tint are
considerably different and the RGB readouts are considerably different. I can then do a "click balance" on the lightest gray and LR now says "Custom" WB and the one
built from the CWB is perfectly neutral and the "as shot" one is no more neutral than the file was to begin with.

Andrew-You said "DNG camera profiles and WB are separate by design."
Apparently they are not so separate. What am I missing and what is your opinion of the DNG profiles worth?

Thanks to you and the others that took time to reply.
CB
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digitaldog

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Re: Xrite DNG Profile and white balance
« Reply #8 on: October 23, 2015, 06:34:24 pm »

What am I missing and what is your opinion of the DNG profiles worth?
Quite a bit within reason.
Quote
In this 30 minute video, we’ll look into the creation and use of DNG camera profiles in three raw converters. The video covers:

What are DNG camera profiles, how do they differ from ICC camera profiles.
Misconceptions about DNG camera profiles.
Just when, and why do you need to build custom DNG camera profiles?
How to build custom DNG camera profiles using the X-rite Passport software.
The role of various illuminants on camera sensors and DNG camera profiles.
Dual Illuminant DNG camera profiles.
Examples of usage of DNG camera profiles in Lightroom, ACR, and Iridient Developer.

Low Rez (YouTube):
http://youtu.be/_fikTm8XIt4

High Rez (download):
http://www.digitaldog.net/files/DNG%20Camera%20profile%20video.mov
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Andrew Rodney
Author “Color Management for Photographers"

Charles Beasley

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Re: Xrite DNG Profile and white balance
« Reply #9 on: October 23, 2015, 07:31:14 pm »

Andrew-thank you so much. I had not seen that in my searches. I should have known you would something like this.
Can't wait to watch it.
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AlterEgo

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Re: Xrite DNG Profile and white balance
« Reply #10 on: October 23, 2015, 11:56:52 pm »

Andrew-thank you so much. I had not seen that in my searches. I should have known you would something like this.
Can't wait to watch it.
do yourself a favor and don't and just simply read A.Torger who actually knows how they are working inside ;)
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