Quote - I am rendering on a Mac - and I cant figure out how the general difference in gamma between Macs (1.7) and MsPCs (2.2)  influence the results - for me everything is too dark (see jestertjuuh) above) - I have to crank up the lights to get fair skin over 100 percent - although the texture itself is fairly pale.

The problem is that we cant discuss this directly - our system setups are too different - so what you see is not what you get on other peoples computers. 

I feel your pain.

From googling I find this:

The Macintosh has built-in gamma correction of 1.4. This means that after the software sends the signal to the framebuffer, there are internal hardware corrections which will further process the signal, specifically by gamma correcting it another 1.4 - That is, the signal is raised to the 1/1.4. Therefore, to get full correction, the software itself should first adjust the signal by raising it to the 1/1.8 power. (2.5/1.4 = 1.8) Thus the system gamma on a Macintosh is 1.8. Note some graphics cards in Macintoshes may have their own software to change the standard gamma and Adobe Photoshop 3.0 is now released with a gamma control panel from Knoll software which allows the user to change the system gamma of their Macintosh. The 1.8 standard is still accepted as the universal Mac System Gamma, but users should be aware that a Mac can be set differently. The Knoll software control panel for the Mac rewrites the look up table, (LUT) with a value of g/2.5 where g is the gamma the user selects. Thus selecting 1.8 will rewrite the LUT with 1.8/2.5 = 1/1.4 - the default setting. (The values in the LUT are 1/1.4 and this is called a 1.4 correction)

So - according to my understanding, an image that looks good on a PC should be TOO BRIGHT for you, not too dark. And your great looking images, viewed on my machine, would be too dark.

In the past, I have observed images from MAC users and felt they were dark on my PC.

If, as you say, you are seeing the opposite, it may be that your graphics hardware+drivers+monitor are doing something non-standard?

Also, if you are viewing an image in Photoshop, and it starts doing what it thinks should be done for colorspace conversion, you may see yet another result.

Here is a random exchange between some folks on another forum that is similar to ours:

On Jan 30, 2007, at 7:55 PM, Eric Herrmann wrote:

    

On Jan 30, 2007, at 4:43 PM, Chris Murphy wrote:

No. gamma is an exponential function. The greater the number, the move curved the tone response curve becomes. So for given image data, a tone response curve defined with a gamma of 2.2 will be darker than the same image with a tone response curve defined with a gamma of 1.8. It's the same idea as "dot gain" for CMYK. More gain, darker image, even though the CMYK values don't change.

Doh! Then I do have it backwards. Well, glad that ColorSync stuff is really working. :)
Seems I've got an even bigger problem if the images uncorrected are displayed darker on Mac than Windows in the first place.

Without display compensation, Mac vs. Windows, the Mac will display the same image with a lighter mid-tone than Windows. If they're darker on the Mac than Windows, then something is screwy.

Thanks Chris for setting me right!

I don't know what to make of this. Perhaps you have one of these utilities in your machine that could fix it?

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