Digital BW, The Print

OK, I've got some concept of how we visually judge a print as warm, cool, or neutral. But is there a standard for neutral?

If I take a decent colorimeter or spectrophotometer, will a neutral print have a=0, b=0 in LAB space, and just positive L values? Or is there more to it than that? Supposedly, the 6 lowest squares of a Macbeth ColorChecker are all a=b=0, with L ranging from 20-96.

I'm working on a profiler for QTR (and other B&W or limitued gamut processes) and it would be able to help if I could set it up for the official neutral rather than just a "good looking" neutral.

Also experimenting with the use of three non-colormetric devices to determine neutrality. The devices are a Status A (Wratten 92, 93, 94 filter) X-Rite 414 print densitometer, Epson 2400 scanner, and Nikon D70 DSLR. They all make good densitometers, as long as we don't stray from gray. I find the camera actually is the best densitometer. I'll describe why in a different post...

For QTR, after generating a neutral curve, I'm going to double the C and M (or LC and LM) curves to get the "warm" tone, so that the 50% position on the slider really is neutral.

Ciao!

Joe

> From: koloshor [mailto:wiz@...]
>
> OK, I've got some concept of how we visually judge a print as
> warm, cool, or neutral. But is there a standard for neutral?
>
> If I take a decent colorimeter or spectrophotometer, will a
> neutral print have a=0, b=0 in LAB space, and just positive L
> values? Or is there more to it than that? Supposedly, the 6
> lowest squares of a Macbeth ColorChecker are all a=b=0, with L
> ranging from 20-96.

It would seem that neutral midtones would be a gray that doesn't change the
color of the light illuminating it, only attenuates it, which is to say
a=b=0. However, papers aren't necessarily neutral, either. So while a=b=0 is
probably a good scientific definition, in practice I'm not sure if prints
don't seem more neutral if the midtone color is chosen to match the paper.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...