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Weblog Entry

Mac Gamma

January 14, 2004

One thing I’m noticing is that colour profiles are crucial when working in Mac Photoshop, even if the final product is meant for on-screen display.

A long-time trick/crutch of mine on Windows was the screen capture. Alt + PrntScrn grabs a shot of the active window to the clipboard, which is easily pastable to a Photoshop canvas. I never even thought about it, I just did, and I did a lot.

Because the Mac handles screenshots a little bit differently (Cmd + Shift + 4 dumps a user-defined area to a PDF file, instead of the clipboard) I’ve had to start importing the screenshot instead of pasting it. This involves a dialogue asking if I want to save or discard the colour profile attached to the document.

I’m getting hung up on this is when I can’t remember which instances require using the embedded profile, and which involve converting to the working space. I’ve configured my default working space in Photoshop to ‘Color LCD’ which seems to keep input and output consistent relatively, but OS X saves each screen shot to ‘Generic RGB Profile’ which produces a mismatch warning. By discarding the profile attached to the file and just using my default colour space, I’m theoretically working with the raw pixels, non-corrected.

comparing gamma

I’m still not confident I’ve got it though. Above is a shot taken as I was struggling to figure out which settings keep the colour consistent. The blues on the top are warmer, almost purple compared to the blues on the bottom. The top shot half is the screen shot, the bottom is the actual dock. Subtle difference, but this can be a big deal when you’re dithering for transparency and colour-matching. Consistency is really important.

It strikes me as rather odd, though, that working solely with on-screen imagery requires such juggling of colour modes. Especially when I never had to think about it on Windows.

update: Brian Warren points out that Cmd + Ctrl + Shift + 4 copies the screen shot to the clipboard instead of dumping it to a file. Pasting that into an open document seems to alleviate any profile matching problems with screen shots. Excellent!


Reader Comments

1
Brian Warren says:
January 14, 02h

Try Cmd+Ctrl+Shift+4 - that gives the selection straight to your clipboard - makes it simpler.

Dave S. says:
January 14, 02h

Well that solves the screen cap problem nicely, and I don’t even have to clean up the PDFs littering my desktop after. Thanks Brian!

The original concern still stands when working with PSDs cross-platform, or opening specific image files. I’m running into color profile warnings far more frequently on OS X.

January 14, 02h

Im switching to Mac at work in just under 7 days. Articles like this one gives me valuable insight into some of the minor differences that will impact my work.

Thanks for a great pointer regarding colour profiles and Photoshop!

January 14, 02h

I run into the same color profile problems when working with screenshots in OS X. Every time I see that dialog box I mean to go searching for a fix… but never do.

So with this comment I offer nothing. Except for relaying the comfort that you are not alone. I’ll be curiously watching this thread…

5
Brian Warren says:
January 14, 02h

You’re quite welcome - and there are a bunch more (), but the problem stands, I agree. I believe it might have to do with the fact that Quartz (mac os x video engine) uses PDF to display everything it shows you - which is why it’s so easy to scale everything, and print anything as a PDF. But also it means that everything you get has some kind of color profile associated with it - it must attach your colorsync profile to screenshots it saves or something along those lines.

Indeed - as I used cmd+shift+4 to get the pdf on my desktop - when I opened it in photoshop it asked if I wanted to use the embedded color profile (in this case, i had “ProTFT 17 Hyp” - the default for this display)

I investigated a bit and if you go to your utilities folder and nose around there there’s the colorsync utility - and it has an option to “specify default profiles… to be used when a document does not contain embedded profiles”. Now I dont do a whole lot of cross-platform work but that might be what’s happening. Maybe not.

6
Brian Warren says:
January 14, 02h

sorry - meant to include a link there in those ()

For more screenshot options than you ever would need….
http://forums.osxfaq.com/viewtopic.php?t=2635

Mike D. says:
January 14, 03h

Additionally, those of you who are used to hitting Command-Shift-3 for the last 15 years to capture your screen can go into the Keyboard Shortcuts Control Panel of Panther and remap Command-Shift-Control-4 (the most useful of the four screen capture commands) to Command-Shift-3.

As for color profile matching, if you only work in web graphics and never deal with calibration for printing presses, go to your File > Color Settings menu in Photoshop and set it to “Emulate Photoshop 4” mode. This effectively renders documents in Photoshop as they would render in any other application. It basically disables all the fancy color-profiling stuff that is great for print but not suitable for web.

Mike D. says:
January 14, 03h

Sorry, that’s the “Photoshop > Color Settings” menu. I’m still trying to shake OS 9 conventions even after having ditched it two years ago.

January 14, 03h

This problem also largely stems from Photoshop’s RGB color management. Long about PS version 5, Adobe decided to make sRGB (developed by or for Microsoft) the standard RGB color space, since the web was becoming big, and “Wouldn’t it be great if everything you saw in Photoshop looked exactly the same as the rest of the world sees it in Internet Explorer on Windows.”

The huge problem is that the sRGB profile, created for Windows, is actually very limited as RGB profiles go. This stems from the fact that because most PC monitors back in the day were cheap, and the Windows default Gamma is about 15 percent less bright than that on a Mac. sRGB is simply a gimp color profile built for a lesser (read: consumer) monitor.

All that said, when Adobe made sRGB the standard, it hacked off a ton of Mac designers who preferred working in the truer color space. Unfortunately, this was dangerous to do, because if you shared your files with someone who didn’t know this, they’d totally kill the color on your RGB image.

Consequently, the Mac default gamma remains it usual bright self, while Photoshop more or less “simulates” the gamma on a Windows box with sRGB.

There are some workarounds, and I myself have been dealing with this issue this week. I’ll see if I find anything else.

January 14, 03h

The other cure is to shut Photoshop’s color matching off all together. Set the color management policies to “Off” for RGB, CMYK and Gray images in the Color Settings dialog. (I also shut off the embedded profile warnings.)

I had to do this to keep colors from chaging when pasting back and forth between Photoshop and Illustrator.

Suzanne says:
January 14, 03h

Not entirely related, but I find the application ImageWell to be very handy for uploading annotated screenshots for reference with others.

http://www.xtralean.com/Products/ImageWell/

It’s not so handy when *I* need the screenshot internally (to this machine) but it’s great for sending screenshots to others.

January 14, 06h

Josh,

I would argue that the sRGB is a much better choice for a Photoshop working space than the monitor’s profile. Remember that even prosumer digital cameras like the Powershot S45 embed (via EXIF data) the sRGB profile – it’s more than adequate unless your a pro photographer, in which case Adobe RGB (1998) is the winner.


This is the best discussion of profiles and color spaces, and all those frightening Photoshop settings I’ve seen on the web:
http://www.computer-darkroom.com/ps8-colour/ps8_1.htm

January 14, 07h

I use the ColorSync settings, which works fairly well as long as I’m awake. ;-)

Don’t forget to make sure you have the right profile set for your display, which is set in the Colour tab of the Displays preferences. Some really weird things can happen otherwise.

January 14, 10h

Probably covered in one of the links above, but one of the shortcuts I’ve been using a lot recently takes a screenshot of any open window you specify:

Hit the typical Cmd-Ctrl-Shift-4 to start the process (cursor turns into a crosshair)

Then hit the spacebar.

Wallah! The cursor turns into a camera, allowing you to select any open window currently in view. You can even capture a full window that’s sitting behind others this way (and the window you select doesn’t even have to be in the foreground application). It’s a bitchin way to remain in Photoshop while getting screenshots of some other application window in the background. Also saves needing to crop the window once its pasted into Photoshop.

And on color profiles, I’m with John Phillips: turn them off completely. It will save a lot of headaches. It’s the first thing I’ve done each time I’ve installed Photoshop for the last few versions. They’re not really needed unless you’re doing hi-res print work and trying to match precise colors. And the defaults will certainly screw you up if you’re doing web work and taking screen caps.

January 15, 01h

The Adobe 1998 profile is by far the best and most practical (other than turning them off).

Complete agreement with all who have said such.

January 15, 03h

In addition to the command+shift+4 to grab a screen shot of any region, and the space toggle to grab a selected window, try holding the control key as you finish your selection. That will take the screenshot to the clipboard rather than to a file. Then, just paste into whatever you want…

I do command+shift+4 (drag region) control (release mouse button) and wind up with a selected region of the screen in my clipboard. Timesaver, and fewer .pdfs to delete…

January 15, 03h

doh. didn’t read comments before posting. sorry for the dupe.

Webb says:
January 15, 03h

I’m the picture editor for the a ‘public service broadcast in the UK’ and had a ding dong with the my writers the other day about this. None of ‘em had calibrated their monitor, and none of ‘em knew what sRGB was.
Most users don’t know or care, still, I guess we should.

about the original tpoic, holding down all four keys is quite hard, You can hold shift+command+4 to bring up the crosshairs, then let go, then simply hold down alt and marquee an area I think.. in panther at least

19
Brian Warren says:
January 15, 10h

Doug- that actually works for any element on your display - such as the dock, the menu bar (oddly enough - the shadow for the menu bar as a separate item), the desktop and icons on the desktop too. Pretty wild feature the spacebar camera thing.

Stephane says:
January 15, 11h

Since Photoshop changed profile and the Mac gained Colorsync, i’ve been confuse.

What I usually do is use the Adobe 1998 profile but sometimes that cause problem between Photoshop and ImageReady. Just make sure you use the same setting between the two.

January 16, 10h

There is a problem using non-uniform workspaces for editing images. In a workspace like Adobe RGB or sRGB a color with equal amounts of red, green, and blue will always be a shade of gray. Not true of non-uniform spaces such as Color LCD.

Also rendering intent for conversions can be important. If relative colorimetric produces unexpected results, then try perceptual. And visa versa.

Working in Adob RGB and converting to sRGB at the very last before uploading to a server seems the best color pipeline IMHO. After converting to sRGB save the image without a profile. Color savvy browsers assume any untagged image to be sRGB anyway so there is no point in saving your image tagged.

Another important thing is to go to the Apple colorsync preferences panel and set CMM to Apple CMM. This will not affect Photoshop which has it’s own color engine. It may however eliminate the weird and unpredictable mismatches the result from letting each profile pick a different color engine. This is the only sane setting “Apple CMM.”

‘Color Management’ by Bruce Fraser et all is worth picking up at your bookstore. It provides software specific information.

January 16, 11h

Quotes taken from various comments, not all from the same person.

“It strikes me as rather odd, though, that working solely with on-screen imagery requires such juggling of colour modes. Especially when I never had to think about it on Windows.”

If you never worried about what the colors looked from one monitor to the next, then yes, you probably never worried about the color consistency issue. 8^)

The point is that there was always a problem long in the past, it’s just that most people didn’t bother with the fact the blue looked fine on their monitor, but slightly purple on a different monitor. If you use your monitor as the only point of reference for the color and don’t care about other displays, then you have no worries.

“The huge problem is that the sRGB profile, created for Windows, is actually very limited as RGB profiles go.”

A bit of history here is that sRGB was developed as a general profile that represented the color gamut that could be displayed within most CRT displays. For that history, read this:

http://www.w3.org/Graphics/Color/sRGB.html

It’s not a bad idea as a general purpose attempt at providing an RGB space that if used on the client rendering side, would do a reasonable job of making the colors seen appear consistent across different CRT monitors.

There was a LOT of arguing over the default RGB space when Photoshop 5.5 came out. I know. I was in the meetings. It was a difficult choice, as once you add color management to the application at the core, a good thing in the long term for many reasons I won’t even begin to go into here, you have to deal with the notion of what to do as the default behavior. We felt for people who knew nothing of color management, sRGB was the best way to go, while the pros who did understand it and had to work with it, would set up their system to their needed workflow anyways.

“sRGB is simply a gimp color profile built for a lesser (read: consumer) monitor…All that said, when Adobe made sRGB the standard, it hacked off a ton of Mac designers who preferred working in the truer color space.”

This is simply an uninformed opinion. It ignore any notion of what “color” actually is at the scientific level, and how it is expressed across various media types.

“The other cure is to shut Photoshop’s color matching off all together.”

If you do this, you will return to a state where what color you see in your design have no correlation to what colors other people see on their display devices. It becomes a total crapshoot.

Of course, unless you use JPEGs on your website, it mostly can be anyway, But by working in sRGB, people on other machines will have a better chance of seeing the color as you saw it.

“Working in Adob RGB and converting to sRGB at the very last before uploading to a server seems the best color pipeline IMHO. After converting to sRGB save the image without a profile. Color savvy browsers assume any untagged image to be sRGB anyway so there is no point in saving your image tagged.”

This seems to make little sense. If you convert an image to sRGB, then save it as untagged, how is that different than just saving it with the tag? Browsers see the profile, and those that do use the tag, those that don’t use sRGB.

As a final note, I will say I’m lagging in my own workflow. I work in Adobe RGB, and save most of my graphics in that format, which is why my site can look a bit dark on other machines. I never bothered settingup my work as sRGB for output.

I’ve just got my blog started, and have spent the majority of my time dealing with MT issues and just getting a blog going. So the color consistency was least on my mind. If you want to learn all there is about color management, read Bruce’s book. He’s a friend of mine, and the expert on the issue.

Here’s the link:

http://tinyurl.com/2wmwg