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Glossary

Digitize

To convert analog information into digital format for use by a computer.

DPI

Dots per inch. Number of dots a device such as a printer can display per linear inch. Most laser printers have a resolution of 300 dpi, most monitors 72 dpi. Photo quality inkjet printers range from 1200 to 2400 dpi. Commercial labs are likely to use a print resolution of around 300dpi. This will give a 2100 x 1500 pixel (3.2 mega pixel) image of 7 x 5 inches.

JPEG

JPEG is a standardized image compression mechanism designed for compressing images. This format is commonly used for images attached to e-mail messages and images on the web. JPEG stands for Joint Photographic Experts Group, the group that established this file standard. It is one of the most widely used formats today and is employed by many digital cameras for storing images. JPEG uses lossy compression, which can damage image quality.

Megabyte

An amount of computer memory consisting of about one million bytes.

Megapixel

A unit equal to one million pixels. The higher the resolution the more pixels in an image and therefore the greater the image quality. Images may look fine on your camera’s LCD display or your computer screen, but megapixel quality becomes more important with prints. Memory card – A storage device used to store data, such as picture and movie files. Available in a range of sizes such as 8 MB, 32 MB, and 256 MB.

Pixel

(PICture ELement) – the smallest element of a digitized image. PPI – Pixels Per Inch. The number of pixels per linear inch is used to describe image resolution. A higher ppi means more image detail and correlates to higher image quality. Monitors display images at 72 ppi, inkjet printers require at least 150 ppi to produce photo realistic prints.

RAW

As in unprocessed. A RAW file contains the original image formation off the scanner before in camera processing. Processing can be done afterwards on a computer using special software. Because RAW has 12 bits of available data you can extract shadow and highlight details which would have been lost in 8 bits / channel JPEG or TIFF format. However RAW formats differ between camera manufacturers and cameras so you need dedicated software.

Resolution

The number of pixels in an image. The higher the number, the higher the image quality.

TIFF

(Tagged image File Format ) is one of the few formats that can support 16 bit colour depth which provides a wider range of colour information than 8 bit per channel scans. So while JPEG only supports 8 bits / channel single layer RGB images, TIFF supports 16 bits / channel multi layer CMYK images. TIFF images can be compressed in a lossless way, internally with LZW or Zip compression or externally with programmes like WinZip. Many higher end digital cameras offer TIFF output as an uncompressed alternative to compressed JPEG. But if available RAW is an even better alternative for digital cameras than TIFF.