RGB: stands for red, green and blue. It is a rich colour space and is used for photographic prints (led, lamda,net prints) and for the internet/web. All computer monitor displays use this colour space. Note that not all prints produced digitally are suitable for re-scanning, as they are intended as an end product. If you have scanned an image and had a print made from this scan (RGB output) you should then have this scan converted to CMYK, have a CMYK proof made, and supply your client both a hard copy proof and digital image on disk. Most magazines will not accept digital files in RGB. Supplying the print as a colour guide is not accurate, as the print is RGB and the file is CMYK so they do not correlate.

CMYK: stands for cyan.magenta,yellow, the K is an old printer's term that represents black. This is a much restricted colour space and is used for all other printing (Inkjet, offset, sheet fed, etc). Generally film separations are required, as many RGB colours cannot be reproduced in CMYK (these are called out of gamut ) it is very important to have a CMYK proof produced, either a digital pre proof or a more expensive film proof to check that colours are accurate and to make any colour corrections required. This proof should be sent with the file to ensure that whoever is printing your job does so accurately. As all monitors are RGB devices it is NOT recommended to approve CMYK colour on screen.

If an image is to be used for publication, the material specifications need to be obtained for that publication to ensure the image reproduces in print the same as the colour proof supplied at completion of the work. These specifications need to include the CMYK set up being used, the full bleed, trim and type area, type of file accepted, max ink density, UCR or GCR percentage, dot gain, black generation, black ink limit.

Often you will need these specifications BEFORE you do any scans. Some billboard printers require file sizes in excess of 300MB and you will only know this if you have acquired this information before ordering your scans.

Other digital terms:

DPI - stands for dots per inch. Generally you scan at twice the value of the line screen being used for printing, most magazines are printed with a 150 line screen hence the standard of 300dpi. Inkjets require less DPI. Since this varies greatly depending on the output device and you are paying for the scan in terms of file size (MB) finding this out can save you money. All monitors display at 72dpi.

MB - stands for megabytes and describes how much data is making up your image.

UCR & GCR - a printing method of achieving density of colour by removing colour and replacing with black ink. The amount of UCR or GCR is dependant on the printing method being used.

Paper Stock: The quality of paper being used in any print job will ultimately determine the quality of your image reproduction. This is why it is important to get the CMYK specifications from the printer, the amount of UCR, dot gain, ink density etc for the particular output device. If you supply the image with a incorrect set up, you will not achieve the maximum quality possible.

Interpolation: is a method of enlarging a file, not recommended as this degrades the image quality. Always scan to the largest size you need so an image can be reduced with no loss of quality.

Recommended File Formats and tips:

JPEG: a compressed file. Do not repeatedly save your image in this format as it is lossy (throws image data away), best suited for email and web and when space is an issue.

TIFF: common file format suitable for all uses, however do not use lz compression (an option when saving in this format) as some programs are unable to open this.