Digital BW, The Print

> Todd, I think that if he uses a 2.2 workspace, he would need to calibrate
> his monitor to 2.2 as well.

Bill 

I'm not enough of an expert on this whole gamma/color management thing to
explain it, but from what I've gleaned it seems your monitor gamma and
workspace gamma are two different things and don't need to match. I better
not say any more about it because I can't really explain it. I know I've
been told that a color management aware program like PS compensates the
screen image so that two well calibrated monitors, side by side, on
calibrated to g1.8, the other g2.2, each displaying the same image in PS,
will look very very similar because PS uses the profiles to compensate. Such
is supposed to be the concept behind color management in the first place.
That said, my tests haven't always born that out so I too am confused.


>  Also, as I understand it, by placing the VM
> curve at the top, you would eliminate the need to set the blend mode to
> luminosity?

No, but remember his question. First off, Roark's curves themselves won't
work as designed if their mode is set to luminosity because then you'd loose
the chromacity effects that are deliberately written into them. They need to
be set to normal wherever they are because they have both a color and
luminosity affective purpose. IOW, the use color to distribute the inks
properly, and they use luminosity to linearize the grayscale. Print a step
wedge using VM inks without Roark's curve applied and you'll see the low end
of the tonal scale is less smooth than with Paul's curves applied - the
smoothness of the VM curve is from the luminosity effect of the curve, the
lack of dots and the distribution of the toner throughout the curve is from
the chromacity of the curve.

Back to the question, which was whether an additional gamma move to the
master channel of Roark's curve would affect the chromatic aspect of it and
the answer is yes, but I doubt it's a big deal.

(Take a color image and open a curves layer and steepen the curve to
increase contrast. You'll see color saturation increase too. That's because
Normal mode uses color and luminosity together. Then switch the mode between
color and luminosity to see the difference between the effect of each.)

So to be pure about it and have your gamma tweak only affect luminosity and
not color, you should make your gamma tweak on a separate layer, and, a) put
it below Roark's curves in Normal mode, or b) put it above Roark's curve in
Luminosity mode.

But really, I doubt it would make much difference in the real world. That's
why I say it's for purists.

Todd


> 
> Bill
> 
> on 2/6/02 1:41 PM, Todd Flashner wrote:
> 
> 
> Don't worry about the Mac "being" gamma 1.8, to my understanding that's more
> convention than anything in the hardware, and even the convention has
> changed. Many highend prepress people, retouchers etc, use AdobeRGB, which
> is gamma 2.2 and even calibrate their monitors to 6500K, gamma 2.2.
> 
> 
> If you want to be a purist, just make a separate adjustment layer for this
> gamma tweak and set it's blend mode to luminosity. That keeps the colors
> from being effected. I always make sure that Paul's VM curves are at the
> topmost layer in the stack, which helps too.
> 
> Todd