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Author Topic: Camera colour profile and LR  (Read 1250 times)

kikashi

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Camera colour profile and LR
« on: February 06, 2017, 02:33:13 PM »

I might consider pushing the blue primary in camera calibration up and taking the blue saturation down...

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Jeremy
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scyth

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Re: Camera colour profile and LR
« Reply #1 on: February 06, 2017, 02:45:00 PM »

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Jeremy

in general you supply a "black box" (called "camera profile") with raw /actually demosaicked first, so not that raw/ digital numbers (R, G, B) which are not color (yet) and it outputs ( basically a code in raw converter is using a LUT table(s) from "camera profile" to do that mapping) a color (= coordinates in some proper color space) ... now 2 different profiles might map the same "RGB" (not a color yet) vector to less or more saturated color (as it is a color now we can talk about it being more or less saturated)... and then "saturation slider" (or sliders) does it "saturation" work... with the colors

this is а very basic and oversimplified explanation
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Tony Jay

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Re: Camera colour profile and LR
« Reply #2 on: February 06, 2017, 04:36:04 PM »

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Jeremy
I would suggest Andrew Rodney's site: digital dog.net for a good overview.

There is plenty else besides.

Tony Jay
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BobShaw

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Re: Camera colour profile and LR
« Reply #3 on: February 06, 2017, 04:58:50 PM »

You calibrate a camera to get ACCURATE colour, not necessarily pleasing colour.
If colour is important to you (fashion, product) then Hasselblad is the answer because it does it by itself in the Phocus raw converter since version 2.9
This gives an explanation.
http://www.hasselblad.com/products/phocus-2-9-colour-calibration/
The process is similar for all cameras really.
There are steps left out of the explanation regarding setting levels because they pop up on the screen.
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scyth

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Re: Camera colour profile and LR
« Reply #4 on: February 06, 2017, 05:51:16 PM »

You calibrate a camera to get ACCURATE colour

absolutely not necessary = you can create a "camera profile" w/ whatever purpose you have in mind  ;D or just because you have an itch to do something ...

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scyth

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Re: Camera colour profile and LR
« Reply #5 on: February 06, 2017, 07:04:38 PM »

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Jeremy

and I think I misread your question - if you are talking about "hue/saturation" sliders in "camera calibration" tab of ACR/LR then here is what happening I think - long time ago Adobe used to have only matrix profiles (and coded inside ACR source code on top of that - no external DCP files were available)...

I think the color transform done by those matrices back then was from from camera RGB digital numbers to cieXYZ(D50) and then simply to ProPhoto gamut for some other work that converter was doing (for example with regular saturation slider, etc)...

so those sliders were allowing for example to fit certain light sources within the prophoto gamut or do some creative mods for those embedded profile - because there were no other tools that could do the job before the color transform was over...

then came various versions of DCP profiles and even tools to build/mod those and nowadays you have (supplied from Adobe) profiles that have some matrix part (ColorMatrix to calculate WB math & ForwardMatrix to transform "whitebalanced" DNs to cieXYZ) and some LUT part(s) - one or two and actual real color transform is pulled by those LUTs, however for compatibility reasons and for cases when you have still colors like certain unnatural LED lights, etc the camera calibration tab was left intact... and in cases when LUTs inside DCP can't for example handle certain light sources (like some extreme blue/neon LED lights) you can use those slider to pull the color back from being clipped at the expense it being desaturated - they still affect the matrix part, not embedded in ACR code but how ForwardMatrix from DCP profile is applied, where it maps camera RGB numbers in cieXYZ colorspace before LUTs from DCP start doing the real color transform...

I certainly can be wrong, but madmanchan (Eric Chan) does not visit this forum anymore it seems...
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BobShaw

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Re: Camera colour profile and LR
« Reply #6 on: February 06, 2017, 10:20:37 PM »

absolutely not necessary = you can create a "camera profile" w/ whatever purpose you have in mind  ;D or just because you have an itch to do something ...
Well I disagree, but each their own.
A profile for any device maps the response of that device, be it camera, scanner, monitor or printer. There is no creativity n the process.
If you decide to make a change to produce another effect then that is an adjustment and there are presets or actions or whatever that you can create for that.
At the other end of the path would you have a printer profile that produced wildly over saturated blue if the monitor showed normal blue? Of course not. If you wanted it excessively blue then you would adjust the image that way in the editing and allow the printer to accurately reproduce that.
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Slobodan Blagojevic

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Re: Camera colour profile and LR
« Reply #7 on: February 06, 2017, 10:57:45 PM »

in general you supply a "black box" (called "camera profile") with raw /actually demosaicked first, so not that raw/ digital numbers (R, G, B) which are not color (yet) and it outputs ( basically a code in raw converter is using a LUT table(s) from "camera profile" to do that mapping) a color (= coordinates in some proper color space) ... now 2 different profiles might map the same "RGB" (not a color yet) vector to less or more saturated color (as it is a color now we can talk about it being more or less saturated)... and then "saturation slider" (or sliders) does it "saturation" work... with the colors

this is а very basic and oversimplified explanation

If that is "oversimplified," I can't imagine what a convoluted explanation would look like. Actually, scratch that - no need to imagine - the above IS the most convoluted sentence I've read in a long while.  :)

scyth

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Re: Camera colour profile and LR
« Reply #8 on: February 06, 2017, 11:08:17 PM »

Well I disagree, but each their own.

with what you disagree ? just take a look @ "camera profles" supplied by Adobe for ACR/LR and name any repro profiles there  ;D

A profile for any device maps the response of that device, be it camera, scanner, monitor or printer. There is no creativity n the process.

but it is - you control (not you mind you, because you personally either don't know how or simply don't have the relevant tools) how profile is build  ;D ... take for example a simple case of C1 - load any camera profile supplied by P1, use Color Editor to do your creative work on it, save the result as a camera profile and use further... as a camera profile... with your creative adjustments there.

If you decide to make a change to produce another effect then that is an adjustment

it is a camera profile, Bob... presets are something entirely different


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scyth

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Re: Camera colour profile and LR
« Reply #9 on: February 06, 2017, 11:16:53 PM »

If that is "oversimplified," I can't imagine what a convoluted explanation would look like. Actually, scratch that - no need to imagine - the above IS the most convoluted sentence I've read in a long while.  :)

people with a talent for deconvoluted writing are absent from this topic unfortunately... and I initially missed the point that OP was asking /apparently/ about the "saturation" sliders in camera calibration tab in ACR... those do serve to modify color transform /either for creative purposes and/or, more often so, to handle clipping of certain saturated colors/ guided by the selected camera profile (instead of creating a new profile or modifying it before using)
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Dave Ellis

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Re: Camera colour profile and LR
« Reply #10 on: February 07, 2017, 12:07:45 AM »

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Jeremy

Hi Jeremy, interesting question. Adobe are probably the only ones who can tell you exactly what is happening under the bonnet of ACR/LR. However i did a little test with a photo of a color checker as shown in the attached shots. The first image is processed in ACR with the standard Adobe profile for my camera. The second has saturation of the blues reduced to -50 in the HSV tab and the third has the saturation of the blue primaries reduced to -50 in the Camera Calibration tab. These saturation scales may not be exactly the same however they are probably in the same ballpark. It seems to me that the HSV tab adjustment is a very targeted adjustment of those colours that are predominantly blue. The Camera profile tab adjustments of the primary colours probably directly adjust the colour profile values (either the forward matrices or the HSV tables or both) and basically affect the colour balance. It has a similar effect on the blues as the HSV adjustment but also has some effect on the other colours.

Dave

PS Just found that there is a similar adjustment to the Camera Profile sliders in the DNG Profile Editor. These adjustments do modify the DCP profile (both the forward matrices and the HSV tables) and have exactly the same effect as the ones in ACR/LR.
« Last Edit: February 07, 2017, 01:19:27 PM by Dave Ellis »
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kikashi

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Re: Camera colour profile and LR
« Reply #11 on: February 07, 2017, 04:17:21 AM »

It seems to me that the HSV tab adjustment is a very targeted adjustment of those colours that are predominantly blue. The Camera profile tab adjustments of the primary colours probably directly adjust the colour profile values (either the forward matrices or the HSV tables or both) and basically affect the colour balance. It has a similar effect on the blues as the HSV adjustment but also has some effect on the other colours.

Thanks, Dave: that's very helpful and addresses my question. It's an issue of focus, it seems.

I shall look at Andrew Rodney's site too.

Jeremy
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Jack Hogan

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Re: Camera colour profile and LR
« Reply #12 on: February 10, 2017, 02:26:53 PM »

I've never understood camera profiles. How does saturation in the profile relate to LR's saturation slider for that colour? What would this suggestion accomplish? Is there something I can read?

Hi Jeremy,

You can read the DNG 1.4.0.0 spec if you have the time and inclination.

There you will find that Adobe brings raw values into a connection color space (XYZD50) via a somewhat linear transformation that they often strive to make non-linear.  However, even if it were truly linear, the transformation is often not 'accurate' enough because of imperfections in the capturing system.  To correct the imperfections, image data in the connection color space is first transformed into ProPhotoRGB, then into HSV.  Once there a 3D look up table is applied to every pixel in order to make color more 'accurate'.  Corrected HSV is transformed back into ProPhotoRGB and from there to XYZD50.  The data may then be given a certain 'look' (you know, standard, landscape, etc.) by going to PPRGB and HSV again, have another looky LUT applied and then back to XYZD50 via PPRGB.  Let's not forget the 'tone' curve that needs to be applied in there somewhere before converting to the working colorimetric color space of choice (say sRGB).

I have no idea whether the HSV controls in ACR/LR refer to the first or second trip to HSV above.  If I had to guess I would say the second because the second is all about 'look' while the first is all about 'accuracy'.

Cheers,
Jack
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scyth

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Re: Camera colour profile and LR
« Reply #13 on: February 10, 2017, 04:29:49 PM »

ProPhotoRGB, then into HSV.

then from RGB representation to HSV representation... HSV is not color space

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