Colour Aim Points Flashcards
Conversion from RGB to CMYK is done via
A look up table (LUT)
When converting RGB to CMYK you must take in the following factors
Dot gain Ink limits UCR GCR Gray balance
Photoshop can be set to convert 2 diff ways
- custom chosen attributes
2. Definition of ICC profiles
What is the default profile used to convert RGB to CMYK
Older SWOP profiles
swop is best used for converting images for sheetfed printing…T or F
FALSE. Swop is used for web offset printing therefor unsuitable for sheetfed printing
Ink colours pallet in Photoshop will
Compensate for known deficiencies in common ink sets (I.e. ratio of CMY) for gray balance & indv colour correction
Dot gain pallet in Photoshop
Specifies the dot gain for press and stock
Can simply be set to MT gain or fine tuned
UCR Stands for
Under cover removal
What does UCR do?
Removes CMY from neutrals and replaces with K
Black is important to image quality & must be controlled more tightly on press
Limits separation of colour and tone in SH
If press can print high TIC
Avoid UCR
GCR stands for
Gray component removal
Unlike UCR, GCR affects
Colour components too
GCR removes
The gray component from COLOUS & replaces with K
In regards to GCR, K in normal separations will only appear
In neutral SH
K in GCR will be apart of
ALL colours even in the HL
How old is GCR compared to UCR
Relatively new
What are the advantages of GCR
Faster make ready
Reduce ink costs
Better wet ink trapping
Easier to control consistency (only 2 colours used to control consistency)
What are the disadvantages of GCR
Not widely accepted by press ppl Black becomes major component of colour Above 50% GCR extends into colours Below 50% GCR affect similar to UCR Too much GCR = causes subtle colour variation too be lost
What is black generation
Used only with GCR
Determines point at which GCR begins based on relative gray values
Ink optimization is
Software which controls the separation of RGB to CMYK or Re separation of CMYK to CMYK
Saves 17-27% ink
What is black limit
Determines darkest possible value of black produced by Photoshop
Affects the SH
Leave at 100% unless total ink limit is set above 300%
What is the UCA amount
Under colour addition
Adds CMY where black is present in a photo
Not desirable in offset printing
