Adobe PHOTOSHOP 5.0 User Manual page 99

You can choose from several Black Generation
settings in the Separation Setup dialog box:
None generates the color separation using no
•
black plate.
The Light and Heavy settings decrease and
•
increase the effect of the Medium setting (the
default). In most cases, Medium produces the best
results.
Maximum maps the gray value directly to the
•
black generation value. This option is useful for
images with a large amount of solid black against a
light background, such as screen shots from a
computer.
Custom lets you adjust the black generation
•
curve manually.
To use the Custom option:
For Black Generation, select an option (Light,
1
Medium, Heavy, or Maximum) that is closest to
the type of black generation you want. This gives
you a black generation curve to use as a starting
point.
For Black Generation, select Custom.
2
Position the pointer on the curve, and drag to
3
adjust the black curve. The curves for cyan,
magenta, and yellow are adjusted automatically
relative to the new black curve and the total ink
densities.
Choosing the ink limits
For both GCR and UCR separations, the black
generation uses the ink limit settings you enter in
the Separation Options area. The total ink limit is
the maximum ink density your press can support.
By default, the Black Ink Limit is 100%; the Total
Ink Limit is 300%. Check with your print shop to
see if you should adjust these values.
Note: In the Gray Ramp graph, these limits
determine the cutoff points for the CMYK curves.
Using undercolor addition
Use the UCA (undercolor addition) Amount text
box in the Separation Options area to compensate
for the loss of ink density in neutral shadow areas.
This additional ink produces rich, dark shadows in
areas that might appear flat if printed with only
black ink. UCA can also prevent posterization in
subtle detail in the shadows. This option is
available only for GCR separations.
Increasing the UCA Amount increases the amount
of CMY added to shadow areas. Values can range
from 0 to 100%. Check with your print shop for
the preferred value. If you are unsure of this value,
leave it at 0%.
ADOBE PHOTOSHOP 5.0 91
User Guide