Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., mwesley250@e... wrote:

> > > You are setting a custom curve for grayscale I assume by printing 
> out 
> > > a step wedge and visually calibrating the screen to match.
> > 
> > ---Correct
> 
> I find that frustrating. Is there an empirical way to do a match? 
> Densitometer readings of printed step wedge to curve?


-----Martin, this is why there is such a thing as a Gain calculation in the printing 
industry. Any service bureau or printer uses a densitometer to calculate 
Density Gain at different points in the scale. 
Here is how it works: 
The instrument is "shown" the paper white and asked to call it 0% - regardless 
of the actual density (which could be 0.06, for example).
Then, it is shown the maximum black and asked to call it 100% - again 
regardless of whether it is 1.65, or 2.2 or whatever.
After the endpoints have been "fed" to the instrument, it determines all points 
in between in percents. So if you read the 5% patch and you get 6%, you 
have a 1% gain. The 85% may well be 95% etc. The darks have more gain 
usually.

The mathematics behind that are based on halftone thinking: A 50% gray, for 
example is defined as any area where half is filled with black ink and the other 
half is paper white. The black half could be broken up by a halftone screen of 
any frequency desired.

Now, when you visit the Custom Dot Gain dialogue in PS6, it will make a lot 
more sense: You are expected to plug in the %numbers by which a given 
theoretical % actually prints. So when you put, say, 90 in the 80% window, 
you are telling the program that our black coverage for that area is 10% more 
than we intend. A square made up of 80% black ink will in fact end up with 
90% ink.

I'll take up your other questions separately, because this is getting a bit long 
as a single post.

Antonis