Colour Management Intro
… user-friendly or do you see red?
How many times have you had a conventional photograph re-printed by a lab and found the colours were nothing like the original? If you didn't supply them with a reference print then they have made a calculated guess on the correct colour, this will be based on their own pre-conceived idea of what the subject should look like. Similarly, when you print a picture which looks stunning on a monitor, it may look different when printed on an ink-jet. The ink-jet doesn’t know how the monitor is displaying the picture so it applies a generic setting, which will give an acceptable result but may not match the colours seen on screen.
Colour Management is a means of producing accurate colour when you scan, view and print images. As your hardware devices all reproduce colour differently, they each need to be calibrated and a profile created for each. With a properly calibrated system, the computer collates the information and ensures that each bit of data (input or output) matches, thereby giving you true WYSIWYG results.
The profiles you create are called ICC profiles. The ICC (International Colour Consortium) is a group of manufacturers of digital imaging products including Adobe, Apple, Agfa, Fuji, Kodak, and Microsoft, that has developed specifications for describing how devices create colour. This information is contained within the structure of an ICC profile. Most hardware manufacturers supply a ready made profile with their unit and whilst this may be sufficient for general work, having total control over your image has to be the ultimate goal.
But is colour management a simple operation or is it more for the techno-freaks? Will it help you, or will it leave you seeing red? In this short introduction we will have a brief look at colour management software, profiles and ways of getting the best possible results from your hardware. I will look at the various options in greater detail in a series on colour management over the following weeks.
The monitor is the central critical item - it’s your visual reference for making alterations to pictures. Whether using Curves, Levels, Contrast & Brightness, or a simple Variations adjustment, they would all be a waste of time if you couldn’t reproduce what you see on screen accurately on a printer. Most users do not have their monitor properly calibrated and are making things more difficult than they need be. Make sure that the monitor has been on for at least 30 minutes before making any adjustments as this allows the CRT tube to warm up and the colours to settle. Keep the room lighting constant (in a domestic environment this may be difficult) and avoid obvious mistakes like the monitor facing a window or a bright light next to the screen. Colour Temperature is also important, a lot of monitors are set by default to 9300K (cool white), whereas photographs are best viewed with a setting of 6500K (daylight), select the correct colour temperature for your monitor.
Adobe Gamma, which is automatically installed with Photoshop, is a small application that helps you colour calibrate and create a profile of your monitor. Launch Adobe Gamma from the Control panel – Start, Settings, Control Panel and double click the Adobe Gamma icon. When using it for the first time select the Wizard and follow the on-screen instructions. At the end of the wizard you are prompted to save the profile. Give it a name which will help you identify the profile type (i.e. monitor profile and date; Monitor-15Dec02). The profile can be altered by running the Gamma application again at any time and you can re calibrate any changes that may have occurred on your monitor. When you start Windows (or Mac OS) the monitor profile is automatically loaded and becomes the default monitor profile.
There are several software packages available that do a similar task; Monaco EZ Color 2, WiziWYG, Colorific, Matchbox and Prove IT. These applications have the facility to use a hardware measuring device called a Colorimeter. This is a sensor that attaches to your screen via rubber suction cups and measurements are taken directly from the screen. The hardware device measures the RGB and White points directly from the screen and creates a monitor profile. At more than £200 these measuring devices are not cheap, but they are the most accurate way to keep your display looking right. For professional digital photographers a Colorimeter Sensor is a must have.
Once the monitor is calibrated, create a profile of your scanner. Most calibration software packages provide an industry standard reference chart called an IT8 Target, (IT8 Targets are also available from Kodak and Agfa and other suppliers). The target is scanned (with the scanners auto settings turned off) and the scanned file is compared with a reference file contained in the Colour management software (or supplied on a floppy disk with the target). The scanner profile is created by comparing the values of the reference file with those of the scanned image and saving them as a profile. The next time you scan an image, don’t make any alterations other than the resolution, ignore any cast etc., just simply acquire a raw scan. Once the profile has been applied in Photoshop the colours correct themselves. Although an industry standard, IT8 targets vary slightly from different manufacturers, so it’s very important to get the correct reference file for your IT8 target. To apply a scanner profile to a scanned image, select Image, Mode, Convert to Profile and enter From: Source Space, To: Destination Space - “your scanner profile” click OK. You will see the image change as it applies the profile.
The printer is the last stage in the workflow chain, the output of your work. It is also the item that causes the most problems. It should be pointed out that a monitor displays more colours than can actually be printed and this accounts for many of the problems. The colours that can’t be printed are known as Out of Gamut colours. These colours can be viewed with a Gamut warning – View, Gamut Warning (Shift + Ctrl + Y). Profiles need to be created for each type of paper you use, generally most people have one or two favourite's and stick with them.
Colour profiles are stored by default in the C:/Windows/System32/spool/drivers/color folder. Right clicking on a profile and selecting Properties will display a panel which displays all the information on the profile and you can also associate the profile to a device. Windows uses its own ICM (Integrated Colour Management) and any applications that make use of this will have access to that profile. However, we should point out that only Windows 98 and Windows 2000/Me/XP take advantage of ICM, Win 95 does not.
Currently there only a few imaging applications that make full use of ICC profiles: Photoshop 5,6,7, and Corel Photo Paint 11; while a handful make a limited use: Corel Photo Paint 9 DCE, and Paint Shop Pro 7. Many of the entry level applications don’t use them but do offer a limited form of colour management, see your manual. To apply a profile in Photoshop 7, set the Working RGB colour space (Edit, Color Setting). To make a print using your new printer profile, in the print dialog box make sure the Printer Colour Management box is unchecked (this stops the printer software applying its own profile), and the Space shows your printer profile, press Print.
Colour Management is a complex subject, but not daunting, if you work with digital images regularly or are a professional photographer, then investing time in learning colour management will pay handsome dividends. Over the next two to three weeks I will go into greater depth on each topic, please use the forum to put your questions and views.
© Vincent Oliver photo-i November 2002