“K” is for Key Plate

Referred to as K in the scope of CMYK, the color black is considered to be the “key plate”. This is the plate that all of the other colors on the press are keyed to.
• text
• image borders
• printed first in order

Screen Angles & Screen Clash

When printing in four color process or simply with more than one color there is potential for screen clash.
• the scanner and computer capture the image
• the imagesetter rasterizes the image
• the result is pixel information / halftone

Line Screen
• printer terminology
• long lines of dots at 90 degrees to each other / halftone
• 150-dot halftone = 150 line screen
• different for different printer types / technology
• different for different paper(s)

Images of More than One Color
• line screens cannot be identical
• moire patterns / screen clash

30 degree rotation rule
• first color at 0 or 90 degrees
• second color turned 30 degrees
• third color turned another 30 degrees

The Fourth Color

So where do we put the fourth color if all our angles are already used?
• cannot go another 30 degree turn
• placement is dependent on the nature of the colors
—black as darkest – yellow as lightest – cyan & magenta in the middle

• yellow is the variable
-moire not visible
-15 degree angle
-vertical / horizontal line

• detectable line angles
-90 degree most obvious (yellow)
-45 degree least detectable (black)

standard angle assignments are
• yellow at 0 or 90 degrees
• black at 45 degrees
• magenta and cyan 30 degrees either side of black
-at 15 degrees
-at 75 degrees

correct application of screens prevents visible moire or screen clash:

Beyond Four Colors

Some common printing techniques that reach beyond the standard practice of 4-color process are:
• Stocastic / Frequency-modulated screens
• Hexachrome
• Pantone Matching System

Stocastic / Frequency Modulated Screens

halftones (different dot sizes / fixed grid system)
stocastic (random dot pattern / varying densities)
• no grids / no screen clash / no moire
• no grids / no risk of moire = limitless colors

Problems / Disadvantages
• requires extremely small dots
• dots too large make image grainy
• dots to small can plug up on the press

Hexachrome and Stocastic Imaging

• six color imaging separations
- CMYK – orange – green
• 600 dpi (dots per inch / NOT line screen)

Hexachrome and Screen Angles

• Orange and Green extend the range of color
• Orange or Cyan (only one occupies the screen)
• Green or Magenta (only one occupies the screen)

Hexachrome and PMS matching

• over 90 % matchable using hexachrome
• minimize / eliminate need to wash presses
• packaging industry leading customer use of this technology

Pantone Matching System

(PMS) and Spot Colors are often utilized for the purpose of achieving non-typical or specialized and higher quality results on the press.
The characteristics of PMS colors are:
• custom mixable formulas
• mixing services / charges
• mixed colors made from the standards
-C M Y K – Yellow 012 – Orange 021 – Warm Red – Red 032 – Rubine Red – Rhod. Red – Purple – Violet – Blue 072 – Reflex Blue – Process Blue – Green
• no exact match for a spot color using process mix
• ideal for two-color work / duotones

Problem Areas Using Pantones

A)Clients use a particular pantone color for their logo, and now want a 4-color brochure / ad / newsletter but don’t want the added expens of running a 5th color so the pantone color will now be converted to CMYK, and of course will most likely not convert accurately.

B)Client understands your problem with the pantone conversion to CMYK and opts for the 5th color. How do you show them an accurate proof.
• Solutions:
-cromalin proofs and dab tests – wet proofs

3)Client goes for the fifth color option on the print run and then wants to see their lovely logo overlap a CMYK image
• Solutions:
- If pantone is solid. – If pantone is a tint / screen

Other Pantone Products

Metalic Formula Guide:
• 204 colors
• relies on hard / smooth / coated surface paper
• varnish use
• spot vs. flood
• before or after

Pastel Formula Guide:
• 126 colors
• minimize waste to custom mixing

Class Exercise: Adding logos or spot colors to image files: DCS2 files Color Separations

Reading Assignment (PREP)

• TEXT: Getting it Right in Print; Chapter 15; pgs 127-132
• TEXT: Getting it Right in Print; Chapter 11; pgs 91-102
• TEXT: A Guide to Graphic Print Production, pgs 101-121