AAMUG Color Mgt Mar2010

Or “Why Your InkJet Printer is Jealous ofYour Monitor”

Steven Bernstein

• Why is the Monitor so happy?• And why the printer is so sad.• Can’t we all just get along?• How can we level the playing field?• Can we predict the output?• And they all lived happily ever after… sort

of.

• Monitor = RGB = Additive = Millions of colors

• Printer = CMYK = Subtractive = Only thousands

• Workflow, workflow, workflow• Photographers, set your white balance• Designers, know your rendering intent• Profile the monitor & linearize the printer• Ability to create predictable results =

Priceless

• Millions of Colors• Backlit looks good• Additive Color Space• May actually display

more color than you can see

• Looks stylish when showing off family photos

• CMYK = Thousands of colors, not Millions

• Subtractive Color Model• Requires proper lighting• Proper ink and paper

may be expensive

• Additive = All colors equal white = Monitors• Subtractive = All colors equal ‘black’ =

Printers

• Additive refers to color that is generate by mixing together colored light to generate a final color. o Used in Computerso Televisionso Portable deviceso Referred to as RGB based on the red, green and

blue colors used to generate the colorso All colors together equals White

• Subtractive color is used by mixing together dyes that prevent reflection of light that then produce a color.

All printed media Photos, magazines and books. Referred to as CMYK based on the cyan, magenta,

yellow and black colors used. All colors together make Black

• The Gamut refers to the various levels of colors that can potentially be displayed by a device.

The 1931 model of the visual spectrum. The Yellow triangle shows what TV can reproduce. The black triangle is what sRGB can reproduce.

• Gamut – a range of colors achievable on a given color reproduction medium [...] under a given set of viewing conditions

Here’s the 1975 version showing the amount of colors different light sources can reproduce. Ever wonder why some monitors cost more than others?

• Lab color space is a color-opponent space with dimension L for lightness and a and b for the color-opponent dimensions, based on nonlinearly-compressed CIE XYZ color space coordinates.

• The real power of Lab is that tones and colors are held separately  - you can adjust one without upsetting the other.

• The LAB color space is also the only "device independent" color space in Photoshop and the only one representing the way the human eye sees color.

• Lab Coloro L= Lightnesso a and b = coordinates of colors in a 3-D ‘space’

represent.• Advantages include

o Tones and Colors are separateo Possible to adjust one without upsetting the

other.o Only "device independent" color space in

Photoshop and represents the way the human eye sees color.

So how do we get an idea of what will print versus what is being shown on the monitor?

Enter the concept of using ICC Profiles to linearize devices.

• For Printerso Intended to help produce the most colors

or widest gamut possible• For Monitors

oDesigned to ensure accurate color representation

• Cameras and scanners, too (input devices)oThat’s what the Custom White Balance is

for• How are these profiles made?

• ICC Profiles are files containing information about the color characteristics of input, display, and output devices. oHave the profiles for a source device and

a destination device?oYou can convert from source device

colors to destination colors on the screenoThis is known as Soft Proofing

• For PrintingoConsistency = Density of inkoCalibration = LinearizationoCharacterization = Building a device

profileoConversion = the ICC Profile in action

• Still curious? Down the rabbit hole…ohttp://www.color.org/

• Buy a monitor calibratoroExample – The i1 LT from X-Rite

(GretagMacbeth)The device is the same as the more expensive package

oThe difference is the software… So…• OpenSource may help

ohttp://sourceforge.net/projects/lprof/ohttp://www.littlecms.com/

• A Wealth of VariablesoPapers (substrates)oTypes of Inks oLighting for viewingoThe Calibration of the input devices

• Bottom line: Check to see if the Device Manufacturer or Place of business offers color profiles!

Gamut Mapping is what linearization is good for. It’s a way to compensate for differences between the colors in the original image and the ability of a printer to reproduce them.

Soft Proofing uses an simulates what the image might look like coming out of a color inkjet printer.

• Monitor = RGB = Additive = Millions of colors

• Printer = CMYK = Subtractive = Only thousands

• Workflow, workflow, workflow• Photographers, set your white balance• Designers, know your rendering intent• Profile the monitor & linearize the printer• Ability to create predictable results =

Priceless

• Why is the Monitor so happy?• And why the printer is so sad.• Can’t we all just get along?• How can we level the playing field?• Can we predict the output?• And they all lived happily ever after… sort

of.

• LCD Monitors and Color Gamutso Source: http://compreviews.about.com/od/monitors/a/LCDColorGamut.htm

• RGB Color Spaceo Source: http://en.wikipedia.org/wiki/RGB_color_space

• Soft Proofing Example and Color Gamut Mappingo Source:

http://blogs.mathworks.com/steve/2008/12/24/soft-proofing-example/o Source:

http://blogs.mathworks.com/steve/2008/11/19/color-gamut-mapping/ • Important Information About RGB and CMYK

o Source: http://www.printingforless.com/rgb-cmyk.html • About.com: Desktop Publishing

o Source: http://desktoppub.about.com/cs/basic/g/cmyk.htm• Wikipedia: Lab Color

o Source: http://en.wikipedia.org/wiki/CIELAB • Printer Profiling- Matching What You See To What You Get

o Source: http://www.signindustry.com/outdoor/articles/2004-07-29-GIA-PrinterProfiling.php3