Dana - Curves correct?

qtr
curves
piezography

#1

Dana-

Here is the linearization off the spreadsheet for Hahnemuhle Photo Rag White 305gm paper I made with the K7 Selenium. The 21 gray step-wedge looks good too in Gamma Gray 2.2.

The QTR Curve Graph shows the dark Cyan to almost max out, with the Matte Black barely shown there. Is this normal, or should I alter the Matte Black (up) and pull back down on the Cyan? I don’t know where the cool selenium color comes in at, the Matte Black or the Cyan shade? I will assume Matte Black for this paper too, although I don’t see a big difference between the PK & MK ink?

Also, in the conversion from RGB into Gamma Gray 2.2 in CS6, there is also something it sometimes asks about some “Working Gray - Dot Gain 20%” or something? Local commercial lab uses that “Dot Gain 20%” in their black & whites off their 9900 through PS when I asked them. Where do you put the “Perceptual, Relative, etc.” (4 settings possible) settings too in the conversion? Leave “Black Point Compensation” checked or not?

Thanks.

Fwiw, I have to uninstall “Adobe Flash” to upload images here for some reason. Otherwise I get red exclamation mark in the pop-up uploader for any images loaded. Might help anyone else having this issue.

Mack


#2

[QUOTE=Mack;4079]The QTR Curve Graph shows the dark Cyan to almost max out, with the Matte Black barely shown there. Is this normal, or should I alter the Matte Black (up) and pull back down on the Cyan? I don’t know where the cool selenium color comes in at, the Matte Black or the Cyan shade? I will assume Matte Black for this paper too, although I don’t see a big difference between the PK & MK ink?
[/QUOTE]

I’m not Dana - but I can tell you that you should not adjust these curves. If you do, you will no longer be linear and most likely very lumpy in the output. If you look at the curves you notice that dMax is not made from black ink, but by adding black ink to three other shades of ink. It is an accumulation of density with linear separation from dMax to the other side of dMin. It is a very careful balance that you should not disturb. To read more about K7 curves - check this out: http://www.piezography.com/PiezoPress/blog/piezography-k7-inks-and-curves/piezography-profiles/
All of the shades of Selenium ink are actually the color of Selenium toning. Shade 7 is as selenium as Shade 6. Our system works by diving an image between seven shades of ink. Rather than using fewer shades of ink and some toning agents, we divide the image into tens of thousands of gray levels. This is how we produce fidelity and extreme resolution. So you can not adjust the color without changing the ink set.

[QUOTE=Mack;4079]Also, in the conversion from RGB into Gamma Gray 2.2 in CS6, there is also something it sometimes asks about some “Working Gray - Dot Gain 20%” or something? Local commercial lab uses that “Dot Gain 20%” in their black & whites off their 9900 through PS when I asked them. Where do you put the “Perceptual, Relative, etc.” (4 settings possible) settings too in the conversion? Leave “Black Point Compensation” checked or not?[/QUOTE]

This means that you have last saved your images files with the Dot Gain 20% as the attached profile. Probably your Photoshop Color Settings for Grayscale is set at default setting of Dot Gain 20%. You should consider changing that to Gray Gamma 2.20 as we recommend in our NEW Piezography Manual. You can select Relative Colorimetric and Black Point Compensation if you are going to convert your legacy images. But, if you change your Photoshop Settings and select the Covert to Working Gray option, the files will be converted for you.

Jon