Dmax and Dmin
Dmax (density maximum) is the densest point on a scale of black to
white. With the PCR II Plus, Dmax is the measurement taken from Box
1 on Test Image #1.
Dmin (density minimum), the opposite of Dmax, is the measurement
taken from Box 16 on Test Image #1.
Dmax and Dmin are determined not only by the PCR II Plus, but also
by the film, processing, paper, and printing. Chrome film, for example,
always has density even if you exposed it to the sun for an hour before
processing it. Every photographic printing paper has a published Dmax
and Dmin for the print side.
An image with a Dmin within 0.02 to 0.04 density units of the
medium's Dmin is probably successful.
To evaluate your Dmax, read some exposed media and compare that
to your test image. Consider the image successful if the Dmax is within
a few density units of the exposed media. Tiny imperfections in the
Dmax are caused by ambient exposure within the PCR II Plus, usually
a result of stray light reflecting from other parts of the test image.
Increments and Channels
While adjusting the color balance of your PCR II Plus, image a series
of test frames with different brightness, contrast, or repeat settings.
Your initial tests should tell you in which direction the curves need to
move, but not the exact combination of settings required to produce
the goal.
If large changes are required, make those changes in increments of 5
units to one channel of either the brightness or contrast values.
Change only one channel a time. If you change all three channels at
once, you will not know which values are responsible for each result.
As you near your goal, use an increment of 2 units.
6-76 • PCR II Plus User Guide
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