When you’re editing, the monitor screen should display colours and tones as close as possible to ‘real world’ values.
The objective of calibration and profiling is to ensure consistent colour reproduction from capture to output.
Windows and MacOS include basic built-in calibration utilities, however their focus is on producing a usable image; not the colour accurate one you need for printing photos or editing video clips.
Calibrating your monitor and creating profiles is the best way to ensure the results of edits will match your intentions.
Monitor screens differ widely in performance and, over time, the brightness, contrast and colour reproduction of even the best monitors can drift. Calibration lets you keep track of the screen’s performance.
The screen grabs above show the effects of calibrating a very out-of-balance screen (top) and the screen after calibration (below).
Calibration tools
Calibration is carried out with a device known technically as a spectrophotometer, which measures light energy at various frequencies from the brightest white to the deepest black and across the red (‘R’), green (‘G’) and blue (‘B’) wavebands. The resulting values are used by profiling software to create a ‘profile’ that characterises the output of the screen.
The two main manufacturers are Datacolor – which makes Spyder calibrators – and X-Rite – which offers i1 and ColorMunki calibrators. Both manufacturers supply the necessary software required for calibration. The process is relatively simple.
This illustration shows the hardware set-up for screen calibration; the measurement device is placed on the template indicated by the software, while an attached counterweight hangs behind the screen. The screen should be tilted back slightly to keep the calibrator in contact with its surface. (Source: EIZO.)
ICC profiles
ICC profiles were established by the International Colour Consortium to describe colour performance by mathematically ‘mapping’ the hue, contrast and saturation output of a specific device (camera, screen or printer). This creates a colour profile that can be used by all devices in the workflow to ensure consistent colour values.
Each profile defines the most saturated colours plus the range of tones the device can reproduce in a specified ‘colour space’ (shown in the diagram below). For a screen, it defines the brightness, contrast and colour values reproduced relative to the screen’s resolution, contrast and gamut (tonal range). A printer profile will specify a precise combination of printer, ink, paper and output settings.
When profiles are consistent, the output will reflect the colours and tones recorded by the capture device throughout the workflow. Without profiles, variations between devices and media will cause faulty colour reproduction.
This graphic shows the gamut (colour range) for a typical monitor used for image and video editing. The sRGB colour space (green triangle) fits comfortably within the boundaries of the monitor’s gamut (red triangle) showing the monitor can display all of the colours used in Web applications. The purple triangle on top of the red triangle shows the screen can cover the Adobe RGB colour space, which is used by most photographers. The blue triangle marks the DCI-P3 colour space, which is used for editing professional video footage.
Monitor profiles are obtained by measuring how the screen reproduces hues and tones relative to a known specification. Printer profiles are specific to the printer as well as the paper and ink that is being used. Using the wrong profile can waste paper and ink.
Each printer manufacturer provides ‘canned’ (pre-loaded) profiles for the papers carrying its brand name, loaded into the printer driver. Manufacturers of third-party papers normally provide them as free downloads on their websites. You can find them easily with a web search by naming the paper brand and adding ‘ICC profiles’.
This screen grab shows part of the list of downloadable profiles for Galerie papers with the Epson 3880 printer. Note the check box for downloading installation instructions.
Screen calibration
Because screens take time to stabilise, you should wait until the screen has been used for approximately 30 minutes before launching the calibration software. All screen calibration instruments work in the same way: the device is suspended in contact with the front of the screen, counterbalanced by a weight that hangs down behind the display. The rest of the process relies on the bundled software.
Calibration begins by setting the gamma (contrast level) for the display (in most cases 2.2 works best), then adjusting the colour temperature to 6500K and establishing the correct black and white point luminance (brightness) levels. Then with the measurement device in place, the software measures how bright key hues are, how cleanly neutral tones (black, white and grey) are reproduced and how the brightness changes with changing input values.
Four frames from the software application bundled with a popular calibrator showing steps in the setting-up process.
It’s a simple operation that guides the user through the process, which normally takes between five and ten minutes. After the measurements are completed, the device is removed and the user is prompted to save the profile. Windows users will typically be prompted to save profiles at: C:/Windows/Sys-tem32/Spool/Drivers/Color. For Mac OS X they are saved in the folder: User Name/Library/ColorSync/Profiles.
Once the profile is stored it will be automatically applied whenever images are opened for editing or printing. This should mean the colours and tones you see on the screen are as close as possible to those that will be reproduced when the image is printed or viewed on another screen.
Image editors like Photoshop list ICC profiles in the Document Profile menu in the Colour Management section of the user interface. In this illustration, the profile for printing Ilford’s Galerie Smooth Pearl paper with an Epson 3880 printer has been selected. (Note the ‘canned’ Epson profiles at the top of the list.)
Some devices also allow users to measure the brightness levels in their workspace before the calibration measurements and take those values into account during subsequent measurements. Note: editing is best carried out in subdued lighting. Make sure no direct light shines on the screen.
Room light analysis lets you see if your workspace is too bright for accurate editing.
Some high-end professional monitors have built-in calibration devices that swing down from the top of the screen at pre-set intervals to check its colour accuracy. They are not as accurate as separate calibrators but provide an easy way to keep screens close to specs in busy workplaces. Re-calibration intervals can be longer with these screens but they still need regular calibration with a spectrophotometer device.
This professional 32-inch 4K monitor is shown with its built-in calibration sensor ‘reading’ primary colours as they are displayed on the screen. A gamut plot of the screen’s colour space can be seen in the lower right corner. (Source: EIZO.)
The advantages of profiling
Having a calibrated and profiled workflow saves time and money when printing images, because you’ll waste less paper and ink when what you see on the monitor screen is as close as possible to the results when the image is printed. It will also be easier to obtain consistent quality from edited prints if somebody else prints your images – or uses them in an online application.
Using profiles
The media (paper) selection panel in your printer’s driver is a fixed list that only contains the names of papers made by the printer manufacturer. The best and most consistent results will come from using these papers.
If you want to use a paper produced by a different manufacture, for example, Ilford’s papers with a Canon or Epson printer, you will obtain the best results if you go to the paper manufacturer’s website and download the relevant profile for your printer and the paper you’ve selected.
If the paper manufacturer doesn’t offer profile downloads, the best approach is to choose a media selection that is close to the inkjet paper you’re using. For example, if you plan to print on a glossy paper, choose the closest of the listed glossy profiles.
Note: We generally advise readers to avoid using third-party media for which profiles are not available. If the manufacturer doesn’t care enough to offer profiles, it indicates they may not care enough about the quality of their media.
Excerpt from Digital Darkroom pocket guide, by Photo Review tech editor Margaret Brown.
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