Adobe PHOTOSHOP 5.0 User Manual page 102

94 CHAPTER 5
Reproducing Color Accurately
Decreasing the dot gain makes the image on-
screen appear lighter, because the dots are smaller.
Increasing the dot gain makes the image appear
darker, because the dots are larger. Changes don't
affect actual data in the image until Photoshop
uses the setting to adjust the CMYK percentages to
compensate for dot gain during the conversion
process.
Specifying dot gain
The CMYK Setup dialog box gives you two ways to
specify a printer's dot gain: by defining a single dot
gain value at the 50% level or by setting up to 13
values along the grayscale to create a customized
dot gain curve for one or more CMYK plates.
If the proof has a significant color cast along its
gray range, then the printer probably has different
dot gain values for each ink. In this case, specify
the dot gain using curves.
To specify the dot gain at the standard 50% mark:
Include a calibration bar with your proof by
1
choosing File > Page Setup and selecting the
Calibration Bars option.
Using a reflective densitometer, take a reading at
2
the 50% mark of the printed calibration bar.
Note: If you don't have a densitometer, adjust the
Dot Gain value until the image on-screen looks like
the proof, and then add that value to your printer's
estimate of the expected dot gain between proof and
final output.
Choose File > Color Settings > CMYK Setup.
3
4 For CMYK Model, choose Built-in.
Choose Standard from the Dot Gain menu and
5
enter the total amount of dot gain from step 2 in
the Dot Gain text box. For example, if the value in
step 2 was 54%, you would enter 4 in the text box,
because the dot gain is 4%.
To specify the dot gain using curves:
1 Include a calibration bar with your proof by
choosing File > Page Setup and selecting the
Calibration Bars option.
2 Using a reflective densitometer, take a reading at
one or more marks of the printed calibration bar.
Note: If you don't have a densitometer, adjust the
Dot Gain value until the image on-screen looks like
the proof.
Choose File > Color Settings > CMYK Setup.
3
4 For Color Model, choose Built-in.
5 Choose Curves from the Dot Gain menu.
Select the plates for which you want to set dot
6
gain curves: Cyan, Magenta, Yellow, Black, or All.
Do one of the following:
7
Calculate the required adjustment, and enter the
•
values (as percentages) in the Dot Gain Curves
dialog box.
For example, if you have specified a 30% dot, and
your printer prints it at 36%, you have a 6% dot
gain in your midtones. To compensate for this
gain, enter 36% in the 30% text box of the Dot
Gain Curves dialog box.