Digital BW, The Print

Hello Seth,

>Sorry, Clayton, I don't really agree with that.  Most things between 
>0 and ~13 in PS are too black for an ink to differentiate -- they're 
>just black.  Same applies to white. Anything above 244-246 is a
>specular highlight;  therefore, just paper white. 

I have to disagree.  First, in pure theory 0 is black and anything
above 0 is not black, and 255 is white, etc.  But that's just theory,
what about practical reality?  In my experience I can see a difference
in a print by shifting a dark area by as little as 2 RGB units (less
than 1%).  In addition, I have on two occasions had people look at my
sample prints and ask something like "How did you get such good
blacks, I use the same ink and don't get that?"  In both cases I
recommended they check the RGB values, and in both cases they reported
back that indeed, the values were around 5 to 7 (looked black on
screen) and when they lowered them to 0 they got the deep black.

As for the whites, when I print in BO an area that is 255 there is
bare paper, no dots.  But if I move it to 254, a few widely spaced
dots appear.  The point here is that the printer and driver are
sensitive to and respond to that small of a change.  Can it be seen
with the eye? 

Well, when I look at a BO print of the the continuous gray scale on
Paul's enhanced gray scale image (the step wedges are too crude - look
at the smooth scale) I can see a continuous lightening all the way to
the edge.  With an 8x loupe I can see the dots getting further apart,
and just before the edge, maybe a 64th of an inch away, they stop. 
The Photoshop densitometer shows this to be the point where it goes
from 254 to 255.

In actual real world practice, I have many times worked with a
contrast curve on an image, made a print, moved a point on the curve
as few as 2 RGB units, and seen a difference in the print (and cannot
see it on screen).  I regularly work on that fine a level in the final
stages of working up an image.  

But don't take my word for it.  Try it.  I don't know what printing
technique you use, but it's easily seen with BO printing.  In the
highlights you can see the dots getting further apart until they stop,
and in the blacks you can see the scale getting darker right to the edge.

Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm