Do the gamma of the monitor and working space have to match?

[john_luke]

I am on a Mac. I was working in ColorMatchRGB and had my monitor calibration system set to a gamma of 1.8. This is the Macs native gamma, and ColorMatch was designed

to render at a gamma of 1.8. Everything was peachy. Now, most of the professional digital cameras have AdobeRGB as a selectable colorspace( no ColormatchRGB available for

digital cameras), and the current US Prepress Defaults in Photoshop are AdobeRGB. I am switching over to AdobeRGB to get in sync with the rest of the world. In an article by

Rich Adams from Graphic Arts Technical Foundation, AdobeRGB was designed for a gamma of 2.2. To be true to AdobeRGB, do I recalibrate at 2.2 and disregard the native

Mac gamma?

[emre]

I don't use Macs, but in PCs you don't have to; the color management system does the profile conversions for you. For your information, there are two color spaces here: one for the monitor, and one for the image. These color spaces can be of different color temperature and gamma. Profile conversion will take care of it.

[ellis_vener_photography]

No . <P>I think "No' is the right answer because I have never heard this be mentioned as an issue by any speaker at the various Adobe Photoshop? seminars I have attended that were sponsored by Adobe, Apple, Epson, Canon and Gretag-Macbeth among others -- or in any of the three or four Adobe Photoshop? related books that I use as references. However I am certainly not going to present myself as an expert in this area. Look to /www.schewephoto,.digitaldog.net or /www.pixelgenius.com (J. Schewe, A. Rodney, M. Evening, B. Fraser, S. Resnick & others.) for a more definitive answer.

[amadou_diallo]

Short answer: No

 

Medium answer:

The monitor and working space gammas serve completely different functions.

Choice of monitor gamma is determined by the setting that allows your unit to

display the smoothest possible gradations. Make or download a greyscale gradient

from 0% (white) to 100% (black). Determine whether calibrating to 1.8, 2.2, or

somewhere in between, shows the least banding/posterization/harsh breaks,

particularly in the shadow regions.

 

Working spaces are grey balanced, one of the reasons for their existence. Use of a

1.8 space like ColorMatch or a 2.2 one like sRGB is determined by your primary

output method. One school of thought is to find a space that displays nearly all of

the colors you can output, without an abundance of colors you cannot output.

Assuming you have a calibrated and profiled display (preferably through a

hardware device), there's no "right" combination of monitor gamma and working

space, only one that fits your workflow. And two calibrated, profiled monitors, set

to different gammas should show very similar images when viewed in the same

working space.

 

Long answer:

Check out Real World Color Management by Bruce Fraser, Chris Murphy and Fred

Bunting. Indispensible reading.

 

Amadou Diallo

[ellis_vener_photography]

I agree with everything Amadou wrote. So does Martin Evening. I hope the following answers your question.<P><I>"Adobe RGB is a good choice as an RGB work space because its 2.2 gamma provides a more balanced, even distribution of tones between the shadows and highlights and this is an important consideration for a 'virtual' RGB editing space. Remember, you do not actually 'see' Adobe RGB. The Adobe RGB gamma has no impact on how the colors are displayed on screen, so long as Photoshop ICC color management is switched on. (do not be) confused by the apparent discrepancy between monitor gamma and RGB work space gamma."<P>--<U>Adobe photoshop 6.0 for Photographers</U>, page 80. </I>

[william_bloodworth]

<p>I addressed this same issue with <a href="http://www.hutchcolor.com/Don.html">Don

Hutcheson</a> some time ago and he confirmed that the discrepancy in monitor gamma

and working space gamma is a non issue because the color management system (whether

it's ColorSync, ACE, or ICM) compensates for the difference in rendering to the

monitor's profile. What I have learned through personal study and experience also

confirms this. The CMM uses the monitor's profile to accurately display the tonal

relationships of the image as it exists in the working space. If you're using

Adobe RGB, the monitor's inherent color space is of smaller gamut and the gamma

is likely different, but a good device profile for the monitor allows the CMM

to "translate" the image coding (intensity values) in the working space

to something that when displayed by the monitor will be an accurate perceptual

rendering of the image in the working space. The colors will be slightly different,

but the tonal relationships will be maintained. The 100% pure and saturated green

of your monitor's color space is different (less saturated) than that of Adobe

RGB. So if you have saturated greens in the image, the greens displayed on the

monitor will be less saturated than those technically (colorimetrically) represented

in the Adobe RGB space. The relationships between the colors though, the perceptible

difference between shades or hues is maintained. This applies to gamma as well

as color. If an image recorded in Adobe RGB (gamma 2.2) was displayed on a monitor

with a Mac (1.8 gamma) without the benefit of ColorSync, it would appear lighter.

The inaccuracy would be greatest at the middle of the tonal range (midtones most

affected). With the color management though, the gamma is essentially remapped

so that what you see on the monitor is an accurate representation, regardless

of what the gamma of the working space is.</p>