K values and Luminance values

Open Discussion
1

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?

Cheers

2

kali curve

3

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.

-Walker

4

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.

Cheers
Gareth

5

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
-Walker

6

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

Cheers
Gareth

7

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

-Walker