Are my images Green?

Started 4 months ago | Questions thread
MiraShootsNikon
Contributing MemberPosts: 638
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Here's the Hitch: LR's develop color gamut is always ProPhoto
In reply to Robin Casady, 4 months ago

Hi Robin,

I still think you're mistaken about something, here.

LR does employ a color space to render the bits of your NEF RAW files in the develop module, even before you've exported your NEF as a TIFF or sent it to Photoshop or another external editor. Obviously, Lightroom has to work this way because you're looking at a color photograph on your screen! RAW bits don't become something you can look at unless the various RGB pixel values can be referenced as colors. That's what a color gamut does--it provides the reference that says "these x,y,z values = this color."

In fact (as another poster mentioned above), LR uses the ProPhoto RGB color space to show you your photograph in the develop module. I'm 99.999% sure you can't change this.

However, I do need to add another layer of complication. Your computer monitor can't show you all the colors of which ProPhoto RGB is capable of displaying, right? So when you look at a photograph in the develop module, you're actually seeing a RAW conversion in the ProPhoto RGB color space that's then converted (via the relational colorimetric method, I suspect), to your monitor's / OS's color space.

How do I know this? Because if I use Lightroom's soft proofing feature, LR will show me with "blinkies" where ProPhoto RGB colors exceed my monitor's / OS's color space. (The soft proofing feature can also show you where / how the ProPhoto RGB colors exceed your printer's color space, or any other you select.)

Your test, above, shows that if you open a RAW file in Lightroom (using ProPhoto RGB, because you don't have a choice) and then output that articulation of color to another, smaller color space (or look at it via your monitor's / OS's smaller color space), Lightroom will employ a relational colorimetric method and give you the sRGB or AdobeRGB colors matching the ProPhoto RGB articulation where they're available. That's good to know, but your test doesn't show anything more.

I kicked off this "fork" of the conversation by noting that different color spaces have different shapes, which therefore means that they articulate color differently--that the same RAW bits will look like different colors if different color spaces are used to render them.

To show the difference in how these distinct gamuts translate RAW bits into color, you need to actually see RAW bits as rendered by the different spaces. If Lightroom is a part of your workflow, you can't ever really do that, because Lightroom will always give you the ProPhoto articulation. Sure, maybe you then later output (or soft proof) to a different color space and thereby match the ProPhoto articulation in a different space where the other space has matching colors--but you're always seeing the ProPhoto articulation.

Someone else with more technical knowledge can chime in, here, but I suspect this is one of the big contributing reasons (though certainly not the only reason) why Adobe RAW conversions look so fundamentally different than OEM Nikon conversions--why even the "color calibration" options don't really match OEM Nikon output defaults. If you process RAW in your camera, for example, you're using either an Adobe RGB or an sRGB gamut to translate RAW bits to color, and both Adobe RGB and sRGB are shaped differently than ProPhoto RGB--so the same RAW bits become somewhat different colors.

I know you aren't "interested" in JPEGs, but for the sake of science and understanding the concept at play: shooting a pair of JPEGs in different gamuts and then comparing the articulations is an easy way to see what I'm talking about, here.

(Shooting a few JPEGs once for sh|ts and giggles won't give you the cooties!)

Anyway, good conversation and food for thought!

Robin Casady wrote:

Stacey_K wrote:

Robin Casady wrote:

Stacey_K wrote:

Things can change drastically when you "convert" depending on which rendering intent you use. You don't mention which rendering intent was used.

And as the other poster said, how can an image that is supposedly in sRGB color space being "converted" to sRGB have colors out of gamut for sRGB? That makes no sense.

I don't use LR, I use capture NX2/export to PS so have no idea what the "working" color space is for LR or really anything about LR. I do know something weird is going on in this workflow as far as color management.

http://www.dpreview.com/forums/post/53976021

I read your other post before I replied.

There is -no possible way- for an image that was actually developed or converted as a sRGB file to then include out of gamut colors for sRGB. Converting a sRGB file to an sRGB should do absolutely nothing. It may have been clipped or posterized from using the wrong conversion intent, but it can't have out of gamut colors in it. That's like saying you found 1.2 gallons of milk in a 1 gallon jug.

You really don't get it. Lightroom 5 does not have a color space for a NEF until it is exported. The color space in Lightroom 5 Preferences is applied when the image is sent to Photoshop. The gamut was checked as soon as it arrived in Photoshop. There was no conversion done in Photoshop before the gamut was checked.

If you have a color chart such as the ColorChecker Passport, photograph it and open it in NX2 then send it to Photoshop in sRGB TIFF 16 bit. Check the gamut in Photoshop before doing anything else.

I'm not sure what you are doing wrong but those examples are a -good example- of a mixed up color management workflow.

Since your converter is now obsolete, you will need to learn another one eventually. Might as well try and understand what is going on here. It is likely to be useful when you switch. That understanding will also allow you back up your claim that it is a mixed up workflow. To make such a claim about something you don't understand is ignorant arrogance.

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Robin Casady
http://www.robincasady.com/Photo/index.html
"Get your facts first, then you can distort them as you please."
—Mark Twain

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