In an ideal world, you would be able to point your digital camera at a subject, take the photo and then make prints that either match reality or improve upon it. But, in the real world, your camera must communicate with your computer which, in turn has to ‘talk’ with your printer. In this process, colour information is passed along a chain and re-interpreted by each device. This chain is known as a ‘workflow’.
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In an ideal world, you would be able to point your digital camera at a subject, take the photo and then make prints that either match reality or improve upon it. But, in the real world, your camera must communicate with your computer which, in turn has to ‘talk’ with your printer. In this process, colour information is passed along a chain and re-interpreted by each device. This chain is known as a ‘workflow’.  The diagram above shows how the source and destination profiles interact to produce an ICC workflow that ensures colours are reproduced correctly throughout the imaging chain. All digital workflows start with a colour space, which is like a language that defines colours in the form of numbers. The most commonly-used colour space is sRGB, which is supported by all cameras, display devices and printers. In other words, they all use the same combinations of numbers to define particular colours.  The illustration above shows how colours can be rendered as numbers. This forms the basis of a colour space. Professional photographers and serious photo enthusiasts who use DSLR cameras or advanced digicams have access to a second colour space, Adobe RGB, which has a slightly wider colour gamut, particularly in the green and blue bands of the colour spectrum. This can provide added accuracy and vibrancy in landscape shots.  The diagram above compares the hues that can be reproduced by the Adobe RGB and sRGB colour spaces. Note the difference between them in the green and blue colour bands. Regardless of which colour space you choose, you must retain consistency throughout your colour workflow. So if you have shot with your camera set on Adobe RGB, this should be the colour space you select for editing and printing to maintain consistent colour reproduction from image capture to printing.  Your image editing software should allow you to set the editing colour space to match the colour space setting on your camera.  If you are using the printer driver instead of your editing software for controlling the colour, you may need to select the correct colour space in the driver interface. Setting Up a Colour Managed Workflow
Step 1: The Camera
Step 2: The Working Environment Make sure no light is reflected off the surface of the monitor and avoid mixed lighting (such as daylight plus a desk lamp). For situations where the ability to assess colour and tonal nuances is important, aim to maintain the same type and level of lighting when you calibrate your monitor as you use when you edit and print your photos.
Step 3: The Monitor Two types of tools are available: software programs and colorimeters or spectrophotometers. Both can be used with CRT screens, which are easier to calibrate because they have more adjustments. LCDs tend to be more stable than CRTs but they usually need to be calibrated with a spectrophotometer (see below).
The most widely available software utilities are Adobe Gamma and QuickGamma. Both utilities are wizard-based and easy to use and both create an ICC profile, which is used by the computer’s operating system as the default monitor profile. The illustrations on this page show the steps used to create a profile in Adobe Gamma.  First choose how you would like to work.  Next select the profile description.  Then adjust brightness and contrast.  Finally, adjust the gamma (contrast) until the two boxes look the same. Entry-level colorimeters and spectrophotometers can be purchased for between $150 and $500. The most readily-available models are the Pantone Huey and Huey Pro, the XRite EyeOne Display 2 and the Datacolor Spyder.  The Huey Pro colorimeter in position on a monitor screen with the wizard-based interface that provides step-by-step instructions through the calibration process.  Successful calibration is indicated on the monitor screen, which also allows you to see how the screen appeared before and after calibration. Each colorimeter consists of a metering device that measures the colour of the light emitted by a PC monitor plus a software application that drives it and creates the ICC profiles that are loaded automatically into the display settings. They all come with step-by-step tutorials to help novice users – and some include a facility for measuring the intensity of the light in the working area and applying it to the calibration.
Step 4: Printing Don’t be concerned if the image shown on-screen in the print preview looks grainy and over-saturated. This is because it’s a ‘quick-and-dirty’ rendition that shows you where the image will be placed on the page. It does NOT use ICC profiles. Most printers will offer a choice of high-speed and normal speed printing. For the best quality prints, select the latter mode – even when proofing images and making test strips (see Test Strips and Proofing Options for information on proofing). Keep an eye on the ink levels monitor – if one is provided – so you can change a cartridge before it runs out. Some printers will stop automatically when this occurs; others continue printing but the image quality suffers when the proper number of inks is not used.  Most photo-capable inkjet printers will display an ink level warning when the level of any cartridge drops below a pre-determined point. Some will also remind you to purchase new cartridges.
Step 5: Evaluation Although professional photographers who work in studios usually install special viewing stations for checking the colours and tones in prints, for amateur photographers, any location that is evenly lit with normal daylight will suffice. The key criteria are that the light be bright enough for you to see all the details in the print (particularly highlight and shadow details) and evenly distributed all over the print’s surface. Avoid viewing prints in direct sunlight – particularly if you’ve printed on glossy paper. Some types of artificial lighting (notably incandescent and halogen) can produce colour casts that may cloud your judgment. However, some photographers find a daylight fluorescent tube comes close enough to simulating daylight conditions – provided the viewing environment itself is relatively neutral. If prints are to be displayed under artificial lighting, you should also check how the print will look under the actual lighting conditions in which it will be displayed. You may need to make some slight adjustments to brightness, contrast and colour balance to ‘optimise’ the print for its viewing situation.
Colour Anomalies in Digital Printing In some cases, stabilisation takes only minutes; in others, prints must be left for several hours until you can be sure the colours are stable. Newer printers usually have shorter stabilisation times than older models and printers from leading photo brands are better than those from manufacturers of office printers. Tests by Wilhelm Research have demonstrated that pigment inks are relatively immune to short-term colour drift. This is one reason why they are favoured by professional photographic printers because being able to see how the colours are rendered immediately after the print is made is critically important to productivity and proofing applications. If colours change after printing, you must wait until the colours stabilise to ensure the print is colour-correct. Metamerism is another factor that can affect inkjet prints. The term refers to the tendency for colours to look different under different types of lighting. Two prints that may appear identical in daylight may look quite different under different types of fluorescent lighting – and also with incandescent or halogen lights. Metamerism was relatively common with older pigment-ink printers but is now relatively rare. Nevertheless, it’s important to evaluate your prints under the type of lighting you plan to display them in.
Calibrating with Colour References Consequently, images that look good on a monitor often fail to print well because colours are less vibrant in reflected light. With a reference card you can narrow the gap between the on-screen view and the print. You can also fine-tune colour accuracy. GretagMacbeth’s ColorChecker cards have long been used by photographers as a colour reference. Prices start at over $100 for the smallest 24-patch reference card and extend to around $550 for a 21.6 x 27.9 mm card with 140 colour and greyscale reference patches. Cheaper ($77) but less versatile, is the Kodak Q13 Colour Separation card. But neither is as versatile as a recent addition to this category from Canadian firm, Pixel Place (www.pixelplace.ca or www.perfect-pixs.com), whose Perfect Pixs cards are much more affordable. The standard three-card kit, which contains colour, greyscale and white balance reference cards, sells for $55, while an A4-sized ‘Natural Colour’ card is priced at $34.69 and an 8-Colour Target Card costs only $15.50. The cards are distributed in Australia by Vanbar. The cards are supplied with a CD containing reference images of each card plus instructions for using them to calibrate monitors. You can also display these reference images on your monitor and compare them with the printed cards to detect colour casts and tonal compression. The cards themselves can be photographed, either in the first shot or before a shooting session, to provide a colour or greyscale reference for the ambient lighting in which the shots are taken. This can be particularly useful in mixed lighting conditions.  Finally, photographing a reference card allows you to assess the accuracy of your camera’s exposure system. If you cannot see differences between the zones at the right end of the greyscale zone reference, over-exposure is occurring. When zones at the left end of the scale appear to merge, correct for under-exposure. Shots of calibration cards can also be used to fine-tune colours and tones when editing images, using the eyedropper tool to select relevant patches in the reference target. Overall, a set of reference cards is one of the cheapest and most valuable tools a photographer can possess.
USEFUL URLs
www.wilhelm-research.com for information on image permanence and the results of tests on the latest printers and media.
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