Curves Settings for Digital Negatives - Darkroom Cookbook

[Dan Rainer]

I'm not experienced with digital negatives, but I picked up a copy of the new edition of The Darkroom Cookbook and there was a very detailed introduction to the process. Overall, it was very informative, but I have one point of confusion.

Steve Anschell recommends building curves for different processes using the curves tool set to "Pinkment/Ink %" mode. This gives input/output on a scale of 0/0 to 100/100. However, on the following page, he lists example process curve coordinates from a variety of different photographers—some of which extend to 255/255. Underneath, he even mentions that the scale is 0/0 to 255/255.

Are all of these curve coordinates built for the "Light (0-255)" curve mode? Or just the ones that explicitly extend past 100? Would I get skewed results if I use the "Light (0-255)" mode for all of them?

 

[koraks]

Are all of these curve coordinates built for the "Light (0-255)" curve mode? Or just the ones that explicitly extend past 100?

I assume the latter. Otherwise Christina's curves would be way weird. Note also that it's only Christina's curves that appear to use the 0-100 scale; all the others are 0-255.

Would I get skewed results if I use the "Light (0-255)" mode for all of them?

Yes, you would get dramatically different results than intended.

 

[MattKing]

I've added a reference to the Darkroom Cookbook to your thread title. Looks like @Steve Anchell hasn't been here on Photrio since September, but you necer know ...

 

[fgorga]

I've been making digital negatives for a long time (15+ years) and have never run into a practitioner who uses anything but the 0-255 (light) scale.

That said, a careful reading of the footnote to the attached table says that these are all 0-255 curves.

 

[Patrick Robert James]

I've used 0-100 in the past when I was using LAB mode for negatives. I've changed the way I make negs these days so I use the regular ol' scale now.

 

[koraks]

That said, a careful reading of the footnote to the attached table says that these are all 0-255 curves.

I read that and concluded it must be an erratum. Just look at the series of Christina's numbers; they wouldn't make sense on a 255 scale. The first one would look like this on base 255:

No way.

 

[revdoc]

If I'm working in 16 bits (and I always am), GIMP will present everything in percent. So all my curves are specified 0 to 100.

Anyway, it doesn't look like a mystery to me. Christina's numbers just need to be multiplied by 2.55 to bring them into line with the others.

 

[koraks]

If I'm working in 16 bits (and I always am), GIMP will present everything in percent. So all my curves are specified 0 to 100.

Yeah, that's a bit of a quirk in Gimp. If you go back to 8 bit mode, by default the curves dialog will become 255-based. I think this can be modified somewhere.

 

[Carnie Bob]

I've been making digital negatives for a long time (15+ years) and have never run into a practitioner who uses anything but the 0-255 (light) scale.

That said, a careful reading of the footnote to the attached table says that these are all 0-255 curves.

I have only used LAB , never ever considered RGB for reading numbers, I find LAB is much the same as a colour enlarger that I cut my teeth on .

 

[Carnie Bob]

Not sure about others here but when I am setting up my process we use a 100 scale chart to read output vs input and adjust.

 

[koraks]

I find LAB is much the same as a colour enlarger that I cut my teeth on .

Makes good sense; you have two color axes and one density axis after all.

Not sure about others here but when I am setting up my process we use a 100 scale chart to read output vs input and adjust.

The number of patches you measure is one thing; the numeric values on the curve is another. The latter really isn't that important; it's very much a potato/potato situation. Btw, I just started playing with Argyll CMS this weekend which allows for enormous flexibility in creating test patterns; I made a (for me) very convenient 160-step pattern that prints on ca. 4x5" and reads easily with an i1Pro.