Achromatic
Colour correction system used in conjunction with a colour scanner that removes a degree of extraneous colour.
Additive colours
The primary colours of light - red, green and blue (the RGB “colour space”) that may be mixed to form all other colours in photographic reproduction and in computer monitors.
Anti-alias
Blending text and image edges into background colour to eliminate the stair-step effect - aliasing - prevalent in bitmaps.
Black point
The point on a scanned image deemed to be the darkest, and set to a CMYK value - C80, M80, Y80 K70 works well.
Choke (Choking)
When trapping colour closing in an area that has another colour inside so the choked colour overlaps, also spreading.
Chromalin
A colour proofing system, usually the final colour proof before going on the press. This is a high quality proof and all corrections and alterations should be made prior to this.
Chrome
See Colour transparency.
CLUT
Colour Lookup Table - a colour indexing system allowing computers to appear to display greater colour depth than they are capable of by rounding a colour value down to one that it can display.
CMYK
Abbreviation for the four processing inks; cyan, Magenta, Yellow and Black. The four process colour inks. Their admixture on the receiving paper creates the illusion of full colour.
Colour
Refers to use of paper other than white and ink other than black. Computer monitors use the RGB colour space and most printers use CYMK. Most colour problems stem from either poor translation between these colour models, limitations in one of the colour models (out of gamut colours), or poor colour separation. Also common is spot colour, in which black ink is supplemented with an additional colour. One way of ensuring that colour fidelity is maintained across the design and printing process is to use a standardised set of colours, usually from the Pantone Matching System.
Colour bars
Appear on four-colour process proofs and used to check registration of all printing colours, dot gain and indicate density and ink evenness.
Colour filling
The method of filling deeply cut, rotary engraved characters with ink, paint, or paste to odd colour or contrast. Also known as paint filling.
Colour Key
A printer's proof usually used for viewing the individual layers of C, M, Y and K, four sheets of coloured acetate, for examining the quality of process colour separations.
Colour negative film
Film that delivers a negative colour image.
Colour Separation (1)
Literally separating the areas of a piece to be printed into its component spot and process ink colours. Each colour to be printed must have its own printing plate. Usually referred to in a photographic sense a colour separation of a photo done either digitally or traditionally on a scanner.
Colour Separation (2)
In photography, the process of separating colour originals into the primary printing colour components in negative or positive form. In lithographic plate making, the manual separation of colours by handwork performed directly on the printing surface. An artist can pre-separate by using separate overlays for each other.
Colour separation (3)
The division of a multi-coloured original or line copy into the basic (or primary) process colours of yellow, magenta, cyan and black. These should not be confused with the optical primaries: red, green and blue.
Colour sequence
Order in which the four process colours are printed, usually yellow, magenta, cyan and black.
Colour value
Tonal value of a specific colour as compared to a greyscale.
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