Glossary of Terms

Digital photography is full of jargon and strange “three- and four-letter words”.  Here is an explanation for some of the technical terms used in articles on this part of the site.

If you come across other terms that don’t make sense hit the comment/reply button and ask.  We’ll do our best!

JPEG

JPEG is a standard file format invented by the Joint Photographic Experts group. A file format that was designed to save computer disk space by throwing away ‘redundant’ image data and approximating colour and tone information in small blocks.
Because they may be compressed, JPEG files are useful for images that are going to be loaded up on the web where small file size gives a speed advantage and where they will be viewed only on computer screens which have relatively low resolution.
On a computer JPEG files are followed by .jpg, for example: _MG_5678.jpg

TIFF

Tagged Image File Format is a standard format for image files that allows for lossless compression. Maximum quality TIFF files may be edited and saved without losing image quality.
Because they a re lossless, TIFF files are good to use when you want to maintain maximum quality for printing.
On a computer TIFF files are followed by .tif, for example: _MG_5678.tif

RAW

The data actually generated by a digital camera’s sensor. Camera makers all use different sensors and different electronics so no two cameras raw files are in the same format. So that images can be manipulated by standard software and printed raw files need to be translated by software into a standard file format before anything can be done with them.
Most digital cameras have an in-built computer that converts their raw image files into JPEG files. Some digital cameras allow the user to save the raw files and convert them to a standard format using a software program (raw Processor) on their desktop or laptop computer. A good raw processor can translate raw files directly into the file format required by a printer without needing to translate the file into JPEG or TIFF.
On a computer RAW files will be followed by a suffix that depends on the make and model of camera that made it: some examples are : _MG_5678.NEF (Nikon), _MG_5678.CR2 (Canon), _MG_5678.ORF (Olympus), _MG_5678.PEF (Pentax), _MG_5678.SR2 (Sony), _MG_5678.RW2 (Panasonic/Lumix)

Megapixels, Megabytes, and print size.

Most fine art prints that are made to be viewed close up, are printed using 300 inkjet dots per inch (300 dpi). You can’t see the individual dots with the naked eye. (By comparison, computer screens typically display images at between 72-120 dots per inch).
If you want to make a 15” X 10” print at 300 dpi your image will be printed with 13,500,000 individual ink dots, 4500 dots wide X 3000 dots high.
The best possible quality print will match each dot in your print exactly, with a corresponding pixel in your image file. In the case of the 15” X 10” above, your image file would have to have been 4500 pixels wide X 3000 pixels high. It would have had a total of 4500 x 3000 = 13,500,000 individual pixels which translates to 13.5 MB of data.
Any image data file that is smaller than 13.5 MB will need to be scaled up (upsized) to make a 15 X 10 print. Most people’s images will be in this situation so image quality is really important.

Colour gamut

vision, sRGB printer

The range of colours that a device can record, or retain, or display.  A digital camera has a very large colour gamut:  it can capture most of the colours that the human eye can distinguish.  An ordinary computer monitor has a very limited colour gamut and is incapable of displaying deeply saturated colours that the human eye can see.  An issue that makes managing colour in digital photography interesting, is that an ordinary monitor is incapable of displaying highly saturated blues, cyans, and greens, that a good colour printer can print.

Colour space

A standardised system for assigning a specific range of colours to numbers so a computer can deal with them.

sRGB

A colour space that assigns numbers to only those colours that can be displayed on most TVs and monitors. Most printers not only easily print all the colours of the sRGB colour space but also many colours that are beyond it.  sRGB is not a good choice of colour space if you wish to print images or if you have, or are going to get, a ‘wide gamut’ monitor.

AdobeRGB

A colour space that assigns numbers to all colours that can be displayed on monitors, and also some more saturated colours that are beyond the colour capability (gamut) of most monitors. AdobeRGB is more suited to images that will be printed.

ProPhotoRGB

A colour space that that assigns numbers to most of the colours of human vision, and some ‘colours’ that are invisible to humans.  It contains most of the colours that current digital cameras can capture.  It is the colour space that’s used ‘behind the scenes’ by Lightroom (default) and Photoshop (if you choose) to avoid the possibility of colour loss during image editing.

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