Colour Management - How It Works - Calibrating and Profiling Colour Monitors
This article is intended to give Mac users a little background information regarding monitor calibration. Please read both your monitor's and calibration software's manual or Help menu. Those PC users who have yet to "switch" may also find it useful. Monitors can be calibrated and profiled to provide quite accurate "soft proofs". This only applies when the correct output (printer) profile has been selected in Photoshop's "Color Settings" and "Proof Setup" menus however! In our experience less than 50% of Designers/Prepress companies have properly calibrated displays!
There are
several excellent monitor profiling packages available. These
are now very
reasonably priced (under £150) and usually include both
the hardware and software. The hardware is a small "puck",
usually a colorimeter,
which is placed
against the screen and measures light and colour. These days
the same kit usually measures both the
older CRT (Cathode
Ray Tube) and newer LCD
(Liquid Crystal Display)
screens, but
check
before purchasing. Also check how many computers on site that
the
software is licensed for. Some more professional (and more expensive)
software will need an optional licence for each computer
"seat". We can recommend the X-Rite
i1
Display 2
(formerly
Gretag MacBeth). We don't sell these, but dealers can be found by
searching the
Internet.
There are cheaper products, but we do not
know of their suitability for high-end calibration. Some software can
also use certain spectrophotometers, such as the i1 Pro, which in
theory at least, may be more accurate than a colorimeter.
Before commencing monitor calibration and profiling, you must check the monitor's basic settings. These are normally accessed via On Screen Display (OSD) software, using buttons on the monitor. The Apple Cinema Displays and iMacs don't have this facility (the software will instead download curves into the Graphics Card). Check the monitor's manual! Normally this OSD menu is more than a bit fiddly! There may be an option to set Colour Temperature, also known as White Point, as it corresponds to the Colour Temperature used to view white paper in your Viewing Booth. It goes without saying that proofs should always be viewed in a Viewing Booth. Initially set this to 5000°K (K for Kelvin) or to D50. This is a starting point only. The monitor's Colour Temperature control will only be approximate.
You may well find that although 5000°K (or the technically more correct D50) is the industry standard for prepress viewing, 5500°- 6500°K may be more appropriate for your monitor and proof viewing conditions. For Photographic work 6500˚K (D65) is normal. The best way to check that Colour Temperature matches that of your viewing booth is to create a "Canvas" of white paper in Photoshop using the correct "Color Settings" for your printing conditions. You then compare this image with that of a sheet of your normal high quality printing or proofing paper in the viewing booth. You should also display high quality images in Photoshop and prints/proofs of the same image in the booth. Pay particular attention to highlight detail and dark shadow areas. You may have to modify Brightness settings in the monitor's hardware. With Apple Cinema Displays the Brightness button can be disabled in the Display Preferences, preventing accidental alterations.
The profiling software's manual or wizard will talk you through the other settings such as Brightness and Contrast. Contrast is normally set to max (theoretically not used on LCDs). Contrast won't be available on Apple LCD's. Write down the numbers you use. You will also later need to set your other monitors to the same settings. All these controls function by adjusting the actual monitor's internal hardware (either manually or automatically depending on monitor hardware), or by sending curves to the Graphics (Video) card.
The software will also ask you to set Gamma. This can simply be regarded as the mid-tone "weight". 1.8 was the traditional starting point for Macs. Nowadays many Mac users prefer 2.0 or 2.2. Some very professional calibration applications have the option to use L* (Luminance curves), such as basICColor Display.
The profiling software will display a series of colour patches on the monitor, while measuring these with the colorimeter. When measuring is complete it will generate a Monitor Profile which it will usually install in the correct place. You should also give it a recognisable name and date, such as "Bobs_MacPro Monitor 20_01_10.icc". It is also advisable to check that the new profile is now the default. In Mac Os X this can be checked with "System Preferences/ Displays/ Color". If you don't have access to calibration kit you can do a very basic visual calibration here. Some calibration software may place the profile in the individual user's account under "Home/Library/ColorSync/Profiles folder". This is a complication of Os X, meaning each logged-in user may need a copy of the profile, especially if they do not have Administrator privileges. In Mac Os9 it can be checked with "Control Panels/Monitors/Color". In Mac Os9 or below (or Windows), before profiling ensure that any "Adobe Gamma Control Panel" or similar, is NOT active. Also check that the resolution and refresh rate, etc. is the optimum. Another thing to check under OsX System Preferences/Universal Access/Seeing/Display/ the "Enhance contrast" slider MUST be set to "Normal" before profiling or results will be very strange.
Note that on a Mac (as opposed to Windows), Monitor Profiles are NOT accessed from within Photoshop, unlike Printer Profiles. The profile will be available to all "ICC savvy" applications, while other applications (web browsers, etc.) will be have improved viewing resulting from the new calibration. Also be aware that Apple Cinema Displays only have hardware Brightness settings, and no adjustment for Colour Temperature or Contrast. Be aware that the Brightness on these (and other brands) is usually factory set to a very high level. This not only gives unnatural results, but causes eye-strain, and perhaps a strain on your wallet by reducing the life of the display! Perhaps also an increase in power consumption? Also be careful to use the "Energy Saver" in System Preferences to turn off the Display when it is idle, which will also alleviate screen "burn-in" from continuously displayed windows, etc.
It may be advisable to use a Colour Management Consultant to work with you and train you the first time you calibrate and profile your monitors.
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Previous Article on Printer Profiling
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