QTR-Quadtone RIP

> On Oct 19, 2017, at 12:21 PM, tubadude06@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> To make sure we are on the same page, let's create a 50% patch in photoshop in gray gamma 2.2, in dot gain 20, and in Lab mode. With the same paper as before, having a dMax of 13 and a Dmin of 97, what should be the printed lab values for each patch?


> I would say the gray gamma 2.2 patch should read L*60,

Let’s assume your linearized your curve with a gray gamma 2.2 target (which is default).

The mid-point between 13 and 97 is (13+97)/2 which is L* 61.5. So L*50 in your 2.2 image would be 61.5 on the paper.

> the dot gain 20 patch should read L*64,

Are you saying that if you had a curve that was linearized for gamma 2.2 and then you printed a dot gain 20 target through that, it would by 64? Why would you want to do this? This is just not needed and will confuse people.

If you linearized a second curve using a Dot Gain 20 target, and printed your dot gain 20 target again through the linearized curve, your Photoshop L*50 would be exactly L* 61.5 on the printed target. Same as the GG2.2 environment. 

> and the Lab patch should read L*55. Correct? 

?? No. LAB is device independent and QTR doesn’t even support it as an output space. So I’m not sure what you mean by “LAB Patch”. In Photoshop? If you printed LAB encoded (essentially gamma 1.0 if QTR supported lab)? Again, not needed for fruitful discussion here.

//

Are you trying to figure out the encoded L* differences between grayscale spaces when an environment is calibrated for one space and you then print a different encoded target through it? If so why and for what purpose?

I think that the continual confusion on this list about grayscale spaces is that somehow they are like “photoshop curves” but they aren’t. They are different. They are just reference points. We’ve all agreed that Gray Gamma 2.2 is our magnetic North Pole and the we’ve aligned all our magnetic devices for that pole. Comparing the degrees from that magnetic North Pole and other poles is not a fruitful discussion. Instead, compare your local environment (a direction of a distant tree e.g.:  the L* in a measured target) to your magnetic North Pole (Gray Gamma 2.2). 

If you want to change your magnetic North Pole (e.g: switching to Gray Gamma 1.0), it’s fine. Just don’t compare it to the old North Pole (gray gamma 2.2) because it gets confusing at that point and does not help you navigate around the world.


Best,
Walker