Digital BW, The Print

> Here's an interesting thought experiment, Say we a printing
> out gray swatches from an inkjet printer.  Each swatch
> is a small square of each grayscale value.  Assuming we're
> talking 8 bit files and printer drivers, we can have only
> 256 possible gray swatches.  If its all perfectly
> calibrated ideally we ought to be able to distinguish
> each swatch.  Now imagine a swatch which is a checkboard
> with two different adjacent gray values, for instance
> 137 and 138 mixed together.  What does it look like?  Is
> it appear as a checkerboard of two different grays or
> does it merge into a new and different 137.5 gray swatch?
> I think the answer is "it depends" ... i.e. how close you
> get to it, got your bifocals on? etc.

It's a good demonstration of perception. For those to lazy to make your own
test targets, go into the Files section of this group and look at Tylers
Zees. It's a series of boxes with Zees in each. It represents 100 tones. I
originally thought that the Zees has a gradient through them, but in fact
they are a solid tone, but the box which houses them has a gradient through
it (5%). So the box, which is a gradient looks solid, unless you see it's
tone relative to the solid tone of the Z.

It speaks to the methodology of a teest which determines our ability to
distinguish between tones. If each tone is compared to the tone directly
next to it and they quite close in density it may be very difficult to
distinguish between the two, but if each is compared to a tone of a
significantly large enough difference you will. That is what gives the
illusion of the Z having a gradient.

Thus, in Tyler's target I dare say it's relatively easy to discern 100 tones
(due to the nonlinearity of our monitors gamma it's easier to see in print
than on screen), but if you took a linear gradient and posterized it into
100 steps I believe it would be very difficult to distinguish between many
of the tones.

Todd