Resolution terminology

PPI - pixels-per-inch
Used to describe scan resolution

SPI - samples-per-inch
Also used to describe scan resolution

DPI - dots-per-inch
Normally used to describe laser printer resolution and often used to describe scan resolution

LPI - lines per inch
Used to describe the number of halftone dots-per-inch in a halftone. Also called "Frequency"

Creating Full-Color Separations in Photoshop

1. Scan image on full-color scanner or acquire image from Photo CD.
a. Scan resolution (ppi, dpi or spi - depending on who´s manual or article you are reading!) needs to be no higher than 1.5 to 2 times the final halftone line count. This rule is based on the final printout to be the same size as the scan. If the scan is going to be enlarged then you will need to scan at a higher resolution to compensate the increased size. If there is text in the image or hard edges a higher resolution will help maintain sharp edges.
b. If the final line count (frequency) is going to be 50 lpi then the scan resolution can be 75 to 100 ppi. (This only applies to halftones and not line art.) If the final printout is going to be enlarged 200% then the scan resolution should be 150 to 200 ppi.
c. If possible enlarge the scan when you do it. This may make the file size too large to fit on a disk if you are going to have the films printed by a service bureau.
d. For better control, place a grayscale next to the image when scanning.

2. Bring scan into Photoshop and adjust scan to compensate for low-end flat-bed scanner deficiencies.
a. Use the Tone Curve and lighten the Shadows and Midtones. Adjust the total curve to give a range of 10% to 90%.
b. Apply Unsharp Masking. A setting of 75%, 1 pixel radius and Threshold of 3 works. If not enough use Unsharp Masking again.

3. Adjust Color Balance. Photoshop generally prints with too much Cyan and this can be minimized at this point. Move the Highlight and Midtones towards Red 20 to 30 units. Use the Info Palette to check for hue error in the grayscale. Compensate for this by adjusting specific tone curves for each color.

4. Adjust Preferences for Inks and Separations. These settings must be done BEFORE converting to a CMYK because Photoshop makes the separations based on the new Ink Separation tables.

Printing Inks

a. Use SWOP Newsprint as a default. These colors closely match Union
Ink True Tones and are the standard for web offset printing. (You can try to make your own "xyY"coordinates by comparing a solid print of each color and adjusting the Hue, Chroma and Value.)
b. Set Dot Gain to 35% for automatic presses and 40% for manual. Separation Setups
a. Use either GCR or UCR. Use GCR when most of the design is a neutral color and light in most areas. Use settings of:
Black Generation: Light
Black Ink Limit: 85%
Total Ink Limit: 240%
UCA: 0

Use UCR when the most important part of the design is black or when there are heavy black areas. Use settings of:
Black Ink Limit: 85%
Total Ink Limit: 240%
UCA 0

5. Convert image to CMYK in Mode Menu.

6. In CMYK mode open Show Channels and display for editing just the CYAN channel.
a. Lighten the highlight end to minimize CYAN in the 10% and 20% areas.

7. In CMYK mode display just the Black channel for editing.
a. Apply additional Unsharp Masking to enhance detail and adjust Tone Curve to darken the 3/4 tone and 90% shadow areas. The"skeleton black" may need boosting in these areas.

8. Print the file to the laser printer. Adjust settings under Page Layout. A large file printout can take 30 minutes to one hour (or more) to print out.

Screen: Set the halftone line count to 55 lpi for manual printing and 65 lpi for automatic presses.
Use an elliptical dot for each color.
Angle:
Use the Photoshop default angles or change to the standard angles of:

C/75¡ M/105¡ Y/60¡ K/45¡ or C/15¡ M/45¡ Y/0¡ K/75¡

Additional options:
C/20¡ M/50¡ Y/5¡ K/80¡

Border: Put a border around just the black if necessary.
Captions: It is helpful to put captions on test files. Print Registration Marks, Labels and Calibration Bars. 9. Print to a high quality vellum paper or to white paper and then do a camera shot to enlarge to the correct size. If you are going to enlarge the image, the line count needs to be higher so when it is enlarged the line count becomes 55 lpi.

Option:

10 Send the file to a Service Bureau to have it printed on an Image Setter on film. The file can be sent as either a TIF or EPS. If the file size is too big, it will need to be put on a Syquest cartridge.
Specify:
Final Film Size
Line Count (lpi)
Film Positive
Right Reading Emulsion Side Up
Registration targets and file information

11. Use properly tensioned screens with 305 mesh for manual printing and 355 for automatic. Take care to hold the dots in the 5% and 10% areas. Print in good register with process colors.

12. If the design needs text and graphics, do all of the above manipulations in Photoshop before exporting into Freehand, CorelDraw or other drawing program. Export as a TIF or EPS file. Add text and graphics and print the file out of the drawing program as a CMYK file. This will print the text and graphics as line work with hard edges. If the file is exported to Photoshop the text and graphics will print as halftones.

13. If a design needs a specific spot color you can pull just the color needed by using the Color Range selection. After you have selected the color with Color Range, you must Save the Selection as a Channel. This new Channel will be a negative and must be Inverted to a positive before printing out.

14. To make a white printer for a design, mask around the design with black and then use Color Range to pull the white (as in step 13). Use Fuzziness to increase the amount of white. Place more white in a design when going on medium colored shirts.

Basic Steps for Simulated Process on Black Shirts
with Adobe Photoshop 3.0

1. Scan the design as normal and adjust the midtones, shadows and unsharp masking the same as for a process color design. (Lighten the midtones and shadows with the Tone Curve. Apply Unsharp Masking 75,1,3). The scan resolution for a normal halftone design doesn't need to be any more than 1.5 to 2 times the final printout line count. A 42lpi halftone doesn't need to be scanned at more than 100dpi (at 100% final size). If the original is smaller than the final size then the resolution needs to be higher.

Important note: If the design has very hard edges or a solid black key-line outline, then the scan resolution needs to be 200dpi or higher to keep the edge sharp when printed out.
2. Make a duplicate of the original file for a work file and save the original.
3. Mask around the design with black so it appears on the monitor the way you want it to appear on the shirt. The masking can be done with the Magic Wand tool, the Lasso tool, by airbrushing with black or by using the Pen tool. If using the Magic Wand, change the Background color to black and just delete the area that that magic wand tool selects.
4. Make another duplicate of the file to use for the underbase. Call this file NAME-W1.TIF.
5. Convert this file to a grayscale using the Mode command.
6. Create the first underbase white. Invert this file (under Image, Map). Using the Tone Curve (under Image, Adjust) remove any slight gray in what should be dead white areas and print the file at a 42 to 55 lpi halftone at a 20 degree angle. This is the main underbase white. Save this file.
7. Create the second highlight white. Using the new underbase white file, make the image very light using the tone curve. The only images remaining should be the highlights of the design. Print this file at the same line count as the underbase white at a 20 degree angle. Save this file as a second white called NAME-W2.TIF.
8. Creating colors. Open up the duplicate file of the original file (in color - with the black mask around it). Using the Color Range feature, place the eye-dropper on the first color you want to select. Use Fuzziness to select more or less of the color. Save this Selection (under Selection) as a new channel, undo the selection (Select and None) and Invert the selection. Print this color at the same line count as in number six and use either the 20 degree angle or an angle 30 degrees off the 20 degrees.
9. Select each additional color the same way.
10. If the design is for a dark shirt color other than black you will need to print black. This black will come from the black of the original CMYK file (the one without the black mask). Before converting to CMYK change the Black Ink Limit setting under Preferences to Heavy. Now convert the file to CMYK. Print out just the black channel.
11. Put the white underbases on a 125 to 180 mesh (the lower mesh is easier for manual printing)