K values and Luminance values

Hi all.

I am calibrating my digital negatives using PDN for kallitype printing.

I have used the software to arrive at a curve that is very close to linear.

However i notice that the negatives are now less dense, especially compared to my negatives for platinum, The highlights seemed blown out before I linearized, now they seem too dark despite the curve suggesting everything is good.

So my question is, what luminance values as density on paper should match which K value in photoshop?

Like what would the ideal luminance value on the page be for 90% k in photoshop for example.

Just trying to get my head around it so I know what the goal is.

Ideally the image in photoshop should have similar tones when printed in different processes right?


kali curve

Are you only looking at the negatives? Because Platinum is a different process and requires different Highlight densities it’s logical that the neg would be less dense for Kallitype. The printed measurement on the screenshot look just fine.


Hi Walker,

I was looking at the printed step tablet.

I was just wondering how luminance on paper relates to the K values as viewed on screen.


That a complicated answer with lots of twists and turns . . . long story short they are related but with lots of different variables that effect that relationship

Thanks Walker, Fair enough. I understand there is a lot of theroy behind this stuff.

Is there a smaller step wedge than the 256 that I can print to check that my calibration isn’t slipping?

My ferric oxalate has changed since adding peroxide to remove base fog and I want to avoid using a lot of palladium


Yes, there are plenty of targets in the piezography community edition.