Digital BW, The Print

In a message dated 6/10/07 10:27:17 AM, jrs2@... writes:


> Will the tweaking to get neutral B&W tones effect the color
> prints...if so, how and what to look for?
> 
Well, if it makes neutrals more neutral, that should effect all colors in an 
appropriate manner, especially near neutrals. Keep in mind that the tiny 
adjustments that are involved in neutralization will be invisibly small in 
saturated colors.
> 
> Also, could you better explain (at least for me) what you are talking
> about in the quote below and what the levers are:
> 
> "...gray ramp following paper white down very evenly (consistant
> addition of the paper white color element all the way down the gray
> ramp); thats what some users would want.  Asking it to make grays
> that don't include the paper component as they move farther from
> white, as you've done here, creates a very even ramp from paper white
> down to neutral near black, with the paper white tint dropping off
> slowly. This is what other users might want. Still other users would
> want it neutral from the top, but that would require using neutral
> paper..."
> 
> Hmmm... I though that WAS a good explanation of it. <G>

Basicly, we think we know what we want for neutrality. But neutal is not 
quite so simple. Once you are working with a tunable system with controls for 
these things, and the ability to measure the results, you learn some suprising 
things.

Lets say your paper is natural, unwhitened, and has a mild yellow tint. If 
you run dead neutral grays, you will be putting blue ink on the paper to 
neutralize the paper tone in most grays, certainly all lighter grays. But at paper 
white, that will end. So your ramp will be literally neutral, up to a 
conflicting (in this example yellow) white tone. Depending how much white there is on 
the page, the eye will be biased to see paper as white, and the neutral ramp, or 
at least its highlight parts, as blue. So dead neutral won't even look 
neutral, and will conflict with paper white as well. 

A better solution is to either add the paper tone to the neutral components 
all the way from white to black (or at least to the point where the black ink 
takes over, you can't really control the tone of black, but its not really 
perceptable either, so its not much of an issue). This gives you a print that is 
"paper neutral" all the way from paper white through the entire gray ramp. The 
first set of measurements I commented on did that.

On the other hand, that might not be what everyone wants. The paper tone need 
to be considered in the lighter grays, so that they don't clash with it, but 
darker tones don't necessarily need that tint. The second set of measurements 
showed that type of ramp, where the paper tint was slowly reduced to neutral 
as it moved from white to black. 

A Kodak gray ramp card shows the literal type of ramp: all patches are 
neutralized, but the paper white patch, and the lightest gray patch next to it, are 
polluted by the yellow of the photo paper, and have a yellow tint. Thats the 
best you can do when attempting to print a neutral gray ramp photographically 
on a nonneutral base, but it doesn't make for an attractive ramp for printing B&
W art photos. Thats why paper white factors in the ramp, one or the other of 
the ways above, offer the best gray ramps to paper white for printing images.

Use a neutral paper, this all becomes somewhat moot, unless you intentionally 
tint or crosstone your image on that neutral paper to add depth, warmth, tint 
contrast, or character.

C. David Tobie
Product Technology Manager
ColorVision Business Division
DataColor Inc.
CDTobie@...
www.colorvision.com




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