Digital Printmaking

Pixels, Dots, and Ink Jets

Rob Paine. Printmaking Is Dead

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Digital Printmaking Using Photoshop

The computer is an amazing and unique new tool for making prints. It doesnt replace the traditional methods of printmaking, nor does it make the processes go any faster. However it is useful for bringing photographic information into prints and for creating four color process images. The basic principles outlined here may be used in conjunction with Polyester Plate Lithography, or ImagOn film (intaglio). The most obvious printmaking technique to be used with digital imaging software is Screenprinting. You may either output digital images onto clear transparencies (for Screenprinting or ImagOn film) or directly onto Polyester Plates. Keep in mind that the software for digital imaging changes constantly - pay attention to the concepts in this book because the details have probably already changed. Use a manual and the help section of your imaging software to get help with specifics. Laser printers heat up and melt toner to the paper/plate in a halftone screen dot pattern. Laser printers work on a VECTOR based system of making dots. They provide the most efficient, cheap, and accurate way to make color separations or halftone dot images for printmaking. Laser printers limit image size (most are only capable of printing an 8.5X11transparency).

To begin you must get an image into the computer. You may start off by scanning a hand drawn image, scanning a photo, or creating an original image with a software program like Adobe Photoshop... This example is a high resolution digital photograph (at least 300 DPI) created by the author.

A Vector based image (SMOOTH)

A Bitmap based image (CHUNKY - made up of little colored pixels)

LASER PRINTER PRINCIPLES

HOW TO MAKE PHOTOSHOP COLOR SEPARATIONS WITH A LASER PRINTER

When using a laser printer in printmaking it is important to control the DPI that the printer uses when it prints out your plate or transparency. Most of the time a 300 DPI printout is what you want - but there are also times when you will want to know how to control the Lines Per Inch (LPI). You must use transparency film made SPECIFICALLY for laser printers, if you use Transparencies made for ink jet printers they will melt in the printer and ruin it (printers cost a LOT of money to fix).

HOW TO USE PHOTOSHOP TO PRINT A PLATE OR TRANSPARENCY WITH A LASER PRINTER

Select the printer under File >Page Setup. Then select File>Print and adjust the variables as needed

This process is fairly simple and straightforward. If all you want to do is get a simple black and white image printed out on a laser printer and use it with ImagOn film, Polyester Plate Lithography, or to make a transparency for screen printing select the print with preview box and adjust the output DPI/LPI to match your targeted process. If you dont care about the size of the dots then just set the printers PDI to 300 in the printer Properties dialog box and send it through. If you want bigger, smaller, or less mechanical looking dots then you will need to control the printers default screen using the Print function in Photoshop.
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Click on the screens button on the menu and uncheck this box.

Check these boxes

L.P.I. - The higher the number the smaller the dot. 70-90 L.P.I. For Litho or Intaglio Printing. 40-60 L.P.I. For Screenprinting.
Adjust the frequency (Lines Per Inch) 4

and the ANGLE

and the SHAPE

Shape - The way the computer makes the dot pattern. Use rounds for Intaglio and Lithography. Diamonds or Ellipses for Screenprinting.

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Go to the PRINT menu. Check the boxes for CORNER CROP MARKS, REGISTRATION MARKS, and LABELS. Click on the SCREENS box. Un-check the USE PRINTERS DEFAULT SCREENS box. Adjust the FREQUENCY (L.P.I.). Adjust the ANGLE for each ink (see the standard halftone screen angles below). Select a SHAPE for the halftone dots. Use rounds or ovals for most applications and squares for screen printing. Click OK. Make sure the paper size and source are set correctly for LETTER and MANUAL TRAY. Click OK. Load the transparency film/plate into the Manual tray on the printer. Go to PRINT. Select COLOR MANAGEMENT and choose COLOR HANDLING> SEPARATIONS. Click OK. and it will print out the 4 CMYK plates on the 4 transparencies/films/plates.

After you have set all the variables for each screen, select Separations under Color Handling. Select Print and the laser printer will print out 4 seperate plates, each one containing the information for each of the 4 colors (Yellow, Magenta, etc..)

STANDARD HALFTONE SCREEN ANGLES

(Using these as a guide will keep the dreaded More pattern from occurring as you print).

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A Dithered halftone image (how a ink jet printer naturally makes dots....

A bitmap halftone image (black and white dots manually created in photoshop - it will print just how it looks on the screen). Accurate 4 color separations usually require a hallftone pattern but it is possible ot experiment with a dithered pattern as well. .

INK JET PRINTER PRINCIPLES

Ink jet printers spray extremely small dots of ink on paper to create highly detailed images (generally using the CMYK colors, but sometimes using 6 or more colors instead of 4) The dots that make up the image are usually hard to see with the naked eye. Ink jet printers use a Stochastic Screen (also called a dither) to print out different values and mix colors out of the process inks. It is difficult to use a dithered pattern to do color separation work. You must turn your gray scale images into a halftone manually to print them out on an ink jet transparency (that just means that rather than letting the printer create the halftone screen FOR you have to make the black and white dots in the file you print from). This is called a BITMAP image. When you convert grayscale images to bitmaps Photoshop makes a halftone black/ white value range in the digital file itself (you may adjust the size of the dots, etc.) To make a simple black and white transparency using an ink jet printer all you have to do is select: mode > grayscale. Then convert the grayscale image into a bitmap by selecting: mode > bitmap. The pattern you choose to use for your bitmap is a matter of personal taste - just print it out on paper to look it over....

For a grayscale image, the computer creates a range of values on the screen by using one of 256 possible grays for each pixel.

The same image as a Bitmap will appear in only two colors: black and white.

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HOW TO MAKE COLOR SEPARATIONS USING AN INK JET PRINTER

The channels palette

Open your image in Photoshop. Convert it to CMYK mode. Go to the CHANNELS pallet and click on the black arrow in the top right hand corner. Select SPLIT CHANNELS. This will convert the four CMYK channels into separate gray scale Photoshop images. In EACH of the four images, select IMAGE> MODE and choose BITMAP. This will turn the gray scale image into a bitmapped halftone screen. Gray scale images are pixel based and create black and white value using 256 colors of gray. Bitmaps use black and white dots only. Select the correct OUTPUT RESOLUTION= 300. Check the halftone screen box. Choose the correct FREQUENCY and ANGLE for the color in which you will print this plate. Choose the correct SHAPE for the color in which you will print this plate. The ink jet printer will now reproduce the black and white halftone pattern with great accuracy at a much larger size than a standard laser printer would be able to print. Go to PAGE SETUP and select the correct size and orientation for the transparency film on which you will print. Make sure you have selected BLACK for the color of ink. Select a resolution= 300 DPI Click OK and select PRINT then click OK.

Click on this menu and select split channels

The four channels of the image will split into separate grayscale files.

Set the resolution to 300.

Adjust these settings as desired.

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HOW TO MAKE A DUO-TONE USING PHOTOSHOP

Photoshop can be a great help for multitone images from photographs or drawings. Take an image and convert it to a grayscale image in Photoshop by selecting Image > mode > grayscale. You should now save your file again as filename grayscale or something else that will help you remember that this is the image you are using for the duo-tone. Select Photoshop > Preferences > Cursors. Check the show color channels in color box.

Convert your image to Grayscale

Convert your image to Duo-Tone Use the curve dialogue to adjust brightness, contrast, etc.

Select Image > Mode > Duotone. You may choose to use a duotone, tri tone or quad tone. Select you colors by double clicking on the color boxes.

Pick your colors! Duo-Tone

Pick your colors! Tri-Tone

After you have made your color selection choose Image > Mode > Multichannel. You may now manipulate each color separately (or two colors - or all of them). The channels may be manipulated in a variety of ways. You may cut and paste images out of or into the different channels. You may fill selections with flat color, no color or tints of the color. You may also use any of the tools in Photoshop on each channel just as if it was a layer (filters, rubber stamp, magic wand). Photoshop changes regularly and the print

After you have converted the duo-tone to a multichannel image you can select either of the layers and manipulate them by electing them in the channels palette.

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Use the Marquee tool. You may knock out areas of one channel to let the others show through.

Make a selection and hit the Delete key. The other colors will show through.

4 You may also add color by selecting a brush and drawing with it on the correct channel. Select a color here. Chose black, white, or any shade of gray.

You may view each color by clicking the eyeball on or off in each channel.

The blue (cyan) plate.

The type tool places text on one or all of the channels, creating a selection that you may knock out or fill with a selected color.

The type tool filled with black.

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setup will look different on other networks so learn to use the help menu to do this in your environment. The general principles for digital color separation output will stay the same but the specifics change with each new Operating System and version of the graphics program. Once the image is completed you can send it to the printer jut like you would any other color separation project.
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