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Author Topic: RAW to Lightroom/ACR  (Read 828 times)

vudiemphuongchi

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RAW to Lightroom/ACR
« on: May 02, 2019, 09:34:27 am »

I'm trying to understand the path that a RAW image takes into Lightroom/ACR.

Does the image pass through the camera profile (Adobe Color for Nikon D850) into the Profile Conversion Space (L*a*b*) then from the PCS to Lightroom/ACR Prophoto?

Or is Lightroom/ACR Prophoto part of the camera profile? 

What role does the PCS play, in other words?
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sandymc

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Re: RAW to Lightroom/ACR
« Reply #1 on: May 02, 2019, 10:28:02 am »

To the extent that Adobe camera profiles have a PCS, it's RIMM, aka a linear space with ProPhoto primaries.
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Mark D Segal

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Re: RAW to Lightroom/ACR
« Reply #2 on: May 02, 2019, 10:41:58 am »

The PCS is part of the computer's Color Management Module (CMM) in the operating system.
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Mark D Segal (formerly MarkDS)
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DP

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Re: RAW to Lightroom/ACR
« Reply #3 on: May 02, 2019, 10:36:50 pm »

nto the Profile Conversion Space

you might want to start with understanding that PCS is not "conversion", but "connection"... get the basics right... and then it is not cieLAB only, can be cieXYZ
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DP

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Re: RAW to Lightroom/ACR
« Reply #4 on: May 02, 2019, 10:50:09 pm »

I'm trying to understand the path that a RAW image takes into Lightroom/ACR.

Does the image pass through the camera profile (Adobe Color for Nikon D850) into the Profile Conversion Space (L*a*b*) then from the PCS to Lightroom/ACR Prophoto?

Or is Lightroom/ACR Prophoto part of the camera profile? 

What role does the PCS play, in other words?

Adobe DNG specification explains what happens along the way - how color transforms are guided by DCP content and there are several of color transforms that happen in a full blown profile - but the very first from raw DNs to a proper color space is to cieXYZ(D50)... RIMM happens later down the road, and "Adobe Color" is not a DCP profile - it is a special kind of ACR/LR "preset" (which Adobe calls "enhanced profile") that works on top of DCP (more about that in http://download.adobe.com/pub/adobe/lightroom/profile-sdk/ACR_and_Lightroom_Profile_SDK.zip )

but not all what happens in the code is guided by the content of DCP profile (and XMP enhanced profile on top of that if selected) - some operations are done by round-trips to lab (like masking ?)

so there is no single space in which ACR/LR performs all the operations - it performs different operations in different color spaces

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Jack Hogan

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Re: RAW to Lightroom/ACR
« Reply #5 on: May 03, 2019, 12:44:24 pm »

I'm trying to understand the path that a RAW image takes into Lightroom/ACR.

Does the image pass through the camera profile (Adobe Color for Nikon D850) into the Profile Conversion Space (L*a*b*) then from the PCS to Lightroom/ACR Prophoto?

Or is Lightroom/ACR Prophoto part of the camera profile? 

What role does the PCS play, in other words?

Hi,

You can find an introductory description of how raw images are rendered and the role of the PCS in section 6 at the following page https://www.strollswithmydog.com/raw-file-conversion-steps/

Jack
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