Color Settings - Gray and Spot Working Spaces

I convert my RAW images to ProPhoto RGB color space (16 bit TIF), and complete my editing of color images in Photoshop with zero issues. My Photoshop RGB working space is set as ProPhoto. Colors are great, I've never had any banding issues, and no noticeable color shifts converting the profile from ProPhoto to sRGB (using perceptual rendering intent) for web output. So far so good

I don't do much work in B&W but I'm confused as to what working space I should choose for Gray and Spot. Currently I have Gray set to Gray Gamma 1.8 and Spot set to the default of Dot Gain of 20%. I'm not sure if I'll ever be using these anyway, but these settings have been bugging me for awhile and I'd like to have a better understanding of the various choices and what to use given that my RGB working space is ProPhoto RGB.

Any help/insight would be appreciated.

Are you certain that you need to worry about those modes? I think the majority of people keep their BW images in RGB mode.

+1 What Damo said. Don't worry about it.

ProPhoto uses 1.8 gamma, while Adobe and sRGB use 2.2 Gamma, but it's irrelevant unless you convert to B&W by using Mode->Grayscale, otherwise just use the B&W adjustment or B&W in your printer driver, or anywhere else really... Anything that works with ICC profiles will always show the image correctly, otherwise it will default to 2.2 gamma. If a device incorrectly interprets a 1.8 Gamma profile as 2.2, it will print dark.

Dot gain is completely irrelevant unless the image is going to a press. To explain what it does anyway, it compensates for the possibility that your image may get darker in print, due to the offset dots blending on the paper stock more than is anticipated. The % amount basically tells the press how much the image should be lightened so that the final image looks right. Unless you work in prepress, ignore this.

Bob_A wrote in post #15212733
converting the profile from ProPhoto to sRGB (using perceptual rendering intent) for web output.

There is no perceptual rendering when converting to sRGB.

http://www.colorwiki.c​om …or_Management_M​yths_21-25

Kolor-Pikker wrote in post #15212881
ProPhoto uses 1.8 gamma, while Adobe and sRGB use 2.2 Gamma

sRGB gamma is not exactly 2.2

https://en.wikipedia.o​rg/wiki/SRGB

Kolor-Pikker wrote in post #15212881
but it's irrelevant unless you convert to B&W by using Mode->Grayscale

Agree. Or when creating a new grayscale document.

I'd set Gray Gamma 2.2 in the color settings and not worry about it.

Thanks guys.

The only time I've work in Gray is when I've outputted from my Nikon film scanner as NikonGray, which is 2.2. Converting from color to B&W I'd use RGB. My confusion came when I read two or three articles stating that ProPhoto is 1.8 Gamma and you should select the Gamma for the Gray working space to match ... which makes zero sense to me since I thought they each should be totally different working spaces (which they are).

René, I'll do exactly what you suggested and set it to 2.2.

René Damkot wrote in post #15213237
There is no perceptual rendering when converting to sRGB.

http://www.colorwiki.c​om …or_Management_M​yths_21-25

Interesting stuff, and I think I've seen you post this before René. This would explain when I tried it out a couple of days ago that I couldn't see any difference. I thought maybe it was just the image I was using (most everything within sRGB gamut) and then just went with what Deke McClelland recommended, which is perceptual for photography.

Sounds like I don't have to update any of my Actions since relative colormetric is used when perceptual is specified anyway.

Kolor-Pikker wrote in post #15212881
Dot gain is completely irrelevant unless the image is going to a press. To explain what it does anyway, it compensates for the possibility that your image may get darker in print, due to the offset dots blending on the paper stock more than is anticipated. The % amount basically tells the press how much the image should be lightened so that the final image looks right. Unless you work in prepress, ignore this.

Nice explanation.

A while back I made this video to show how the gray and color working spaces affects channel operations:

http://www.youtube.com​/watch?v=7HX9UJA3rEQ

Good point. It also affects the readouts in the info palette and gamut warning:

See "Possible pitfalls" (scroll down)
http://www.getcolorman​aged.com …nagement/pscolo​rsettings/

Redcrown wrote in post #15213913
A while back I made this video to show how the gray and color working spaces affects channel operations:

http://www.youtube.com​/watch?v=7HX9UJA3rEQ

More interesting stuff, although I may have to watch your video a couple more times to get a better grasp of your findings.

So, from what you and René have posted it looks like your setting for the Gray working space can have an impact when editing an sRGB, aRGB or Prophoto RGB image. So, based on your work were you able to determine the best default for the Gray working space? Would you use the same Gray default if using ProPhoto or sRGB?

I only used one test image, but it looks like the gray-scale image that is displayed when selecting the red, green or blue channels is close to identical for a ProPhoto RGB and sRGB image if Gamma=2.2 is used for the sRGB image and Gamma=1.8 is used for the ProPhoto image. Interesting, although I'm not certain when my editing skills will ever be at a point where I'd make use of the information and where setting a Gamma of 1.8 over 2.2 will make a difference in my workflow. Since I edit using ProPhoto RGB, and since setting the Gray working space to Gamma = 1.8 gives the same results for the red, green or blue channels as Gamma = 2.2 for sRGB, it looks like 1.8 is the "better" default setting.

BobA, I think there may still be some confusion.

When doing "normal" editing of an image, the setting for the Gray working space will not make any difference. By "normal" editing I mean using adjustment layers, filters, blend modes, and maybe masks drawn by hand with the paint brush. It is only when you do channel operations that the Gray working space makes a difference. Even then, that difference may be not be significant.

For example, a tutorial may tell you to copy the red channel as a new layer and change the blend mode of that red channel layer to softlight or overlay as a way to increase contrast. The result of that channel operation will vary depending on both the Color and Gray working space settings. However, if you then adjust the opacity of that layer to taste, you may end up with the same result because your taste will likely lead to different opacities.

This is how I discovered the differences that the Gray working space makes. I was trying to follow a tutorial using a sample image that the author provided. I kept getting results different from the tutorial. It took me a long time to figure out that the author was working in a color and/or gray working space that was different than mine.

As for your conclusion that ProPhoto at Gray Gamma of 1.8 gives the same RGB channel values as sRGB at Gray Gamma 2.2, I think that's not correct, or may have just been a coincidence of your test image.

When you convert an image from ProPhoto to sRGB, all the RGB values will change. The amount of change depends on where the values fall inside the gamut of both colorspaces and what rendering intent you use to do the conversion (relative colormetric, perceptual, etc.).

Redcrown wrote in post #15217849
As for your conclusion that ProPhoto at Gray Gamma of 1.8 gives the same RGB channel values as sRGB at Gray Gamma 2.2, I think that's not correct, or may have just been a coincidence of your test image.

When I made the statement I was basing that only on using channel operations and what I see for the red, green and blue channel (resulting gray scale displayed image) results. I could see that for the RGB channel the different settings for the Gray working space made no difference whatsoever.

What I observed seems to agree with the advice given on a few of the web articles that I've read, where they recommended Gamma = 1.8 for the Gray working space when your RGB working space is set to ProPhoto. I don't really think I'm going to be in a situation where it's really going to matter for me, but since I also couldn't see why anyone would recommend 1.8 I started this thread.

Your video and Rene's link show that that the Gray working space setting does matter and does give different results (for channel operations, using gray scale color picker, etc.) depending on your RGB working space.

http://www.luminous-landscape.com …ex.php?topic=22​239.0;wap2

http://www.adobe.com …dfs/phscs2ip_co​lspace.pdf

http://www.schewephoto​.com …hop/CM-for-BW-Sidebar.pdf

http://www.luminous-landscape.com/tutorial​s/prophoto-rgb.shtml This quote is useful: "Note:Adobe RGB is Gamma 2.2 while ProPhoto is 1.8, thus explaining the different depth of the black area in the Granger chart)"

http://www.photoshopes​sentials.com/essential​s/rgb/

Here's a quote from Jeff Schewe's new book, The Digital Negative: "I changed the RGB working space to ProPhoto RGB and altered my gray working space to a gamma of 1.8 (which for a photographer working with both RGB and grayscale images is useful)."

Unfortunately he never describes WHY it's useful or necessary.