When printing graphics to a inkjet or laser printer, the graphic(s) resolution rarely needs to be more than 360 DPI.
If you send a higher-resolution graphic to your printer than is needed, the image is reduced to a resolution that your printer can handle. With a very large image (2 GB or larger), you may see a "Print failed due to program error" alert message and the print job may not complete.
Reducing your graphics to the maximum resolution that your printer can print can also improve print speed. Sending larger images to your printer may mean that the Mac or the printer must scale the image before printing.
If you want to calculate the byte size of your image, you can use these formulas:
- For graphics based on 8-bit RGB component:
- 3 x DPI x DPI x height x width
- For graphics based on 16-bit RGB component:
- 6 x DPI x DPI x height x width
- For graphics based on 8-bit CMYK component:
- 4 x DPI x DPI x height x width
- For graphics based on 16-bit CMYK component:
- 8 x DPI x DPI x height x width
- For graphics based on 8-bit grayscale component:
- 1 x DPI x DPI x height x width
- For graphics based on 16-bit grayscale component:
- 2 x DPI x DPI x height x width
Inkjet and laser printers use a process called halftoning to approximate the colors in your image. Because of this, the maximum useful image resolution is typically 1/4 (one-fourth) the advertised resolution of your printer. For example, a printer that advertises a resolution of 1440 DPI does not require graphics with more than a resolution of 360 DPI.
Halftoning approximates colors by printing a pattern of dots that, when viewed from a distance, look like the original color. Modern printers use very small dots so you have to look very closely to see them.
The graphic below shows shades of cyan from white to full saturation. In the first graphic pixel zoom we see no printer dots of cyan, which represents a graphic pixel of white. The next graphic pixel zoom shows 25% of the printer dots having a cyan dot, making for a graphic pixel of 25% cyan saturation. The halftone process adds more cyan dots until all the dots are filled with cyan. An 8-by-8 matrix of printer dots will make 1 graphic pixel capable of 64 shades of cyan. Note: Printer software will slightly randomize the location of these dots to help smooth out gradients and so forth.
Note: 360 DPI is a good general recommendation. Check the printer's documentation and printer manufacturer's website for more information about the maximum resolution for printing graphics.