Adobe photoshop cs2 Manual De Usuario
190
ADOBE PHOTOSHOP CS2
User Guide
For example, suppose you are printing to an imagesetter with a screen frequency of 85 lpi and the ratio of the final
image to the original is 3:1. First multiply 85 (the screen frequency) by 2 to get 170. Then multiply 170 by 3 to get a
scan resolution of 510 ppi. If you are printing to an inkjet printer with an optimal resolution of 300 dpi, multiply 300
by 3 to get a scan resolution of 900.
image to the original is 3:1. First multiply 85 (the screen frequency) by 2 to get 170. Then multiply 170 by 3 to get a
scan resolution of 510 ppi. If you are printing to an inkjet printer with an optimal resolution of 300 dpi, multiply 300
by 3 to get a scan resolution of 900.
Note: Different color separation procedures might require different ratios of image resolution to screen frequency. It’s a
good idea to check with your service provider or print shop before you scan the image.
good idea to check with your service provider or print shop before you scan the image.
To calculate the file size before scanning an image
You can create a dummy file to predict the file size needed for the final output of your scan.
1
In Photoshop, choose File > New.
2
Enter the width, height, and resolution of your final printed image. The resolution should be 1.5 to 2 times the
screen frequency you will use to print. Make sure that the mode you plan to scan in is selected. The New dialog box
displays the file size.
displays the file size.
For example, suppose you want the final image to be 4 inches wide and 5 inches high. You plan to print it with a
150-line screen using a 2:1 ratio, so you set the resolution to 300. The resulting file size is 5.15 MB.
150-line screen using a 2:1 ratio, so you set the resolution to 300. The resulting file size is 5.15 MB.
To produce the scan, enter the resulting file size in your scanner settings. Don’t worry about resolution or image
dimensions. After you have scanned the image and imported it into Photoshop, use the Image Size command (with
the Resample Image option deselected) to enter the correct width and height for the image.
dimensions. After you have scanned the image and imported it into Photoshop, use the Image Size command (with
the Resample Image option deselected) to enter the correct width and height for the image.
See also
Optimizing the dynamic range of the scan
Keep in mind that the human eye can detect a wider tonal range than can be printed. If your scanner allows, set the
black and white points before scanning a file to produce the best tonal range and capture the widest dynamic range.
Then use Photoshop’s color adjustment tools to set the white and black points for the scanned image.
black and white points before scanning a file to produce the best tonal range and capture the widest dynamic range.
Then use Photoshop’s color adjustment tools to set the white and black points for the scanned image.
See also
To eliminate a color cast introduced by a scanner
If your scanned image contains an unwanted color cast, you can perform a simple test to determine whether the cast
was introduced by your scanner. If so, you can use the same test file to create a color-cast correction for all images
scanned with the scanner.
was introduced by your scanner. If so, you can use the same test file to create a color-cast correction for all images
scanned with the scanner.
1
Make sure that your monitor has been calibrated.
2
Open a new Photoshop file to create an 11-step wedge. Choose a size from the Preset menu in the New dialog box.
Make sure the size is large enough for the step wedge to be reasonably scanned. The resolution should be at least 240
pixels/inch. You can set the Color Mode as RGB and the Background Contents as either Transparent or White.
pixels/inch. You can set the Color Mode as RGB and the Background Contents as either Transparent or White.
3
Use the Linear Gradient tool
to create a blend from pure black to pure white.
4
Choose Image > Adjustments > Posterize, and posterize the blend using 11 levels.
5
Print the 11-step gray wedge on a black-and-white printer, and then scan it into Photoshop.