Below are some tips for scanning or saving images for press printing in different colour formats:
Full Colour/4 Colour Images
All full colour digital photos and raster images need to be saved in CMYK format, preferably as “eps”. Resolution for full colour images must be a minimum of 262ppi (pixels per inch) or up to 300dpi when saved at 100% actual size.
Greyscale Images
Greyscale images (or black and white photos) need to be saved in “tiff” format at a minimum of 300ppi (pixels per inch), when at 100% actual size.
Bitmap/Line Art Images
Line art, text or bitmap images need to be saved as “tiff” format, with a minimum of 1200ppi (pixels per inch) when at 100% actual size.
All scans and digital photos must be created at the above mentioned resolutions originally, as re-sampling to a higher resolution at a later stage will not increase the quality. The only way the resolution may be increased at a later stage, in some cases, is if the image is originally much larger than the actual size required. In reduction the pixels per inch may be increased in proportion.
Note: “ppi” (pixels per inch) and “dpi” (dots per inch) are similar terms. Different programs may refer to either one.
To print pictures with enough quality the electronic file needs enough information to do so. Web/internet images have a resolution of 72dpi for screen viewing only, and are not suitable for press printing. They appear pixelated and unclear in print.
