Color management: Implementation part 2:
Monitor profiling, workflow details
by Norman Koren

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Table of contents

for the Making Fine
Prints series

Getting started | Light & color
Pixels, images, & files | Scanners
Digital cameras | Printers | Papers and inks
Monitor calibration and gamma
Printer calibration | Scanning | Basic image editing
Black & White | Matting and framing
Tonal quality and dynamic range in digital cameras
Color management
Introduction
Implementation part 1 | Setup
Working color space | Profile anatomy
Implementation part 2
Monitor profiling & calibration | Workflow
Summary | GretagMacbeth Colorchecker
Obtaining and building profiles
Evaluating printer color and ICC profiles



or Image editing with
Picture Window Pro
Introduction | Making masks
Contrast masking
Tinting and hand coloring B&W images
Example: Sunset, Providence, Rhode Island
Thanks to Dennis Wilkins and Jonathan Sachs for excellent suggestions and extensive proofreading.
The series begins with an Introduction to color management and color science. Implementation part 1 describes how to set up color management and interpret the contents of ICC profiles (files that describe the color response of a device or a color space). It features Picture Window Pro, but also includes information on Photoshop. Implementation part 2 (this page) discusses monitor profiling and workflow details. The series continues with Obtaining ICC profiles and building them with MonacoEZcolor and Evaluating printers and ICC profiles.

Monitor profiling and calibration

To properly calibrate and profile your monitor, your video card should have a color lookup tables (LUT). Most recent cards have them. If yours doesn't, go out and get one that does-- even inexpensive cards have them nowadays. If that isn't practical, consult the Color Management tutorial, pp. 19-26, for options.

This is a good time to clarify the distinction between monitor calibration and characterization (or profiling).

Windows recognizes a Default monitor profile, which is used by most LUT loader programs and some image editors, though its existence has no immediate effect on monitor calibration. You can find the Windows default monitor profile by one of two routes. Open the Control Panel, then click on Display, Settings, Advanced, Color management. Alternatively, right click on the screen background (wallpaper), then click on Properties, Settings, Advanced, Color management. The Current monitor, the Default monitor profile, and a list of ICC profiles associated with the monitor are displayed.

There is a good deal of confusion for a simple reason: Monitor profiles often contain information used by LUT loader programs to calibrate the monitor; hence they play a role in both calibrating the monitor and characterizing it. And the characterization stored in the profile plays a role in altering the image sent to the monitor, as shown below.


Image flow from memory to monitor.

There are two places where an image can be altered on the way from the image editor to the monitor.

The best way to learn how monitor calibration and profiling affect the display is to try out different settings. I recommend downloading the calibration chart on the right and opening it in your image editor. It is a powerful diagnostic tool that provides an accurate indication of gamma and black level. Instructions can be found in the Monitor calibration page. The chart works for monitor display only, not for hardcopy. For color I've included simulated GretagMacbeth ColorChecker charts in two color spaces, sRGB and Adobe RGB (1998), at the bottom of this page.

Several programs calibrate and profile monitors. These include MonacoEZcolor, Colorvision SpyderPro with OptiCAL, and GretagMacbeth Eye-One Display, and Profile Mechanic - Monitor. These programs are described in more detail in the Monitor calibration page. All of them measure the monitor with a colorimeter, then create a profile with instructions for loading the LUT. This profile is set as the Windows default monitor profile. Shortcuts to their respective LUT loader programs are placed in the Windows startup directory. I have MonacoEZcolor, which installs MonacoGamma as its LUT loader.

The LUT can also be loaded ay other programs: QuickGamma (which I recommend for beginners who don't yet have colorimeter-driven software), Adobe Gamma (installed with Photoshop and run from the Control Panel), and video driver software. These are discussed in the Monitor calibration page.

Monitor profile glitches: Some monitor profiles have incorrect values for gamma in their TRC (Tonal Response Curve) tags, described above in Anatomy of a profile. I've encountered two cases of interest.

Beware of generic monitor profiles. It's always a good idea to check the TRC tags in monitor profiles with ICC Profile Inspector, especially if you see inconsistencies in the display gamma. Another glitch: MonacoGamma doesn't always work after my ATI Radeon video driver software has been used to set the LUT. Adobe Gamma works more consistently. Since both these programs use the vcgt tags in the Windows default monitor profile, I use Adobe Gamma when I need to set the LUT after I've booted (using the profile created by MonacoEZcolor). Are we having fun yet?

Images in non-ICM aware programs are assumed to have the sRGB color space. No gamut mapping takes place when they are sent (through the LUT) to the monitor. This works reasonably well because CRT monitors are fairly close to the standard sRGB profile, sRGB IEC61966-2.1.

Monitor viewing conditions (a review)  Since one of the principal goals of color management is to produce prints that match the monitor image, correct monitor viewing conditions are vital. More detail can be found in Monitor calibration.
  • Your monitor should be operated in subdued light; dark areas of the screen should appear dark to the eye.
  • Set your monitor's color temperature (white point) to 6500K, D65, or sRGB, which is equivalent to 6500K. The 5000K setting appears too dull and yellow on most CRT monitors.
  • Your display adaptor software should be set to 24 or 32 bit color (True Color).
  • I use a SoLuxDesk Task Lamp with a 4700K 36 degree 50W bulb for viewing prints. The SoLux has a CRI (color rendering index) of 0.98. At the 6500K monitor setting, a white sheet of paper viewed under the SoLux lamp looks a tiny bit yellower (warmer) than white areas on the monitor screen. This is not a problem since the eye adapts quickly when moving from the monitor to the print.
  • Alternative lamps: Two promising choices are Ott-Lite's 18W VisionSaverTM series, which has a color temperature of about 5300K and CRI = 0.95, and Sunwave 5500K fluorescent bulbs, which come in both tubes and compact screw-in models, have good brightness and CRI = 0.93. The Philips 287813 15 watt screw-in daylight compact fluorescent bulb: 5000K, CRI = 0.82, is available at Home Depot, SKU #652746, about $15. It's quite bright. Other compact fluorescents: Sunwave, SunPro, Panasonic, and Verilux. I keep a halogen desk lamp nearby to see what the print will look like in typical indoor lighting.
  • Set the Contrast to maximum unless the image is too bright or harsh.

  • Adjust gamma, the parameter that describes the nonlinear relationship between image pixels and monitor brightness, and Brightness (black level) using the Gamma and black level chart. Several procedures are available. There is some interaction between brightness and gamma adjustments, so you may have to go back and forth between them.

Color management workflow details

Once you've chosen appropriate settings, you can ignore color management most of the time, but there are instances where you need to pay attention. Refer to the diagram below for the big picture. (To be added: manual adjustments with scanners and digital cameras. Update Photoshop print)
  • Attaching or changing color profiles. You may need to attach a profile to an image or change its color space, for example, when you are working in a color space other than sRGB and need to prepare the image for the Web. To change an image's color space in Picture Window Pro, click on Transformation, Color, Change Color Profile... This brings up the dialog box shown on the right. You can choose between three Change options.

  •  
    • Image Data and Profile Setting (the default) is shown. This is the setting you'd use to convert from one color space to another.
    • Profile setting only. Used to tag an image that had no profile setting or an incorrect profile setting: For example, Canon's File Viewer Utility can convert RAW images to Adobe RGB (1998), but it doesn't tag the image files. This makes errors almost inevitable, since untagged images are (by default) assumed to be sRGB. 
    • Image data only Rarely used, but you might find it instructive when you're learning about color management.
    The Print dialog box (the last box you see before printing starts; right) asks you for the printer profile (below). These two entries appear only when color management is enabled. Your answer is not saved. I would prefer to be able to enter a default printer profile in the Color Management Settings dialog box, then have to option of overriding it when I print. You must be certain that your printer driver settings are identical to the setting used to create the profile. You should save them with a similar name.
If color management is enabled and your image files are in color spaces other than None or sRGB, you must use a custom pofile; you should not print with Color Adjustments as detailed in Printer calibration. If you don't use a custom profile the printer driver will assume the image data is in sRGB color space. Images in larger gamut spaces will appear unsaturated.
Printing with Photoshop 7 by John Fellers  (I occasionally get questions on the subject.)
In Photoshop 7.1 there are two techniques for applying ICC profiles to color managed prints. I have used both successfully on the Epson 5500 and 2200.

The first method (which I no longer use) is,

  1. Click on Image -> Mode -> Convert to Profile to change the image's working or source profile to the paper profile.
  2. Go to 'Print with Preview.' Make sure 'Show more options' is checked. Change the drop down list to 'Color Management' and set the destination profile is to 'Same as source.'  Typically, select Perceptual rendering intent. If your image has out-of-gamut colors, you might want to try Relative Colorimetric.
  3. Click on 'Page setup.' Select the correct paper size and paper source.
  4. Click on Printer/Properties, turn off color management (very important), and make sure that the correct media type is selected.
I learned this method at a seminar last year given by Printing & Imaging Association Mountain States.

My preferred method is to not change the working space of the image to the paper space. I use the above method except that I keep the Adobe RGB (1998) working space and enter a custom profile in the destination working space field (in the Color Management dialog.)

The Epson Australia RGB Print Guide PS7 (Windows version) and Mac version cover printing with Photoshop 7. The earlier Epson Australia RGB Printing Guide (Windows version) and Mac version cover printing color_management_2.html Photoshop 6.

.Workflow summary

A diagram of a color-managed image flow is shown below. It's not simple, but I've tried to structure it to be somewhat comprehensible. Boxes that represent sources or destinations and boxes that alter color have distinctive appearances. See the Legend at the bottom. A simplified version is above.


Back to Implementation part 1: Setup, working color space, profile anatomy
Color management and color science: Introduction
Implementation part 2: Monitor profiling, workflow details
Obtaining profiles and building them with MonacoEZcolor | Evaluating printer color and ICC profiles

GretagMacbeth ColorChecker test pattern

This chart is widely used for matching photographic images. I offer these two downloadable images to help you learn color management-- so you can see what happens when you convert between color spaces with different rendering intents, etc. To take full advantage of these charts, you'll have to purchase an original. The pixel values calculated by Bruce Lindbloom from measurements of a new ColorChecker with a calibrated X-Rite 938 spectrophotometer. According to Bruce, GretagMacbeth's own data, printed on the sheet that comes with the ColorChecker, is not colorimetrically meaningful.
 
1. SMPTE-240M embedded profile (same as Adobe RGB 1998).  All colors are within gamut. You can check the pixel values, copied from Bruce Lindbloom's table for Adobe (1998), with the PW Pro eyedropper.

The colors in this chart should look undersaturated in web browsers, which are not ICC aware, but they should look correct-- nearly identical to the sRGB image below-- in a properly set up ICC-aware application.

Simulated GretagMacbeth ColorChecker Adobe RGB (1998) color space
2. sRGB.  Cyan (third row, right) is out of gamut. Colors were derived by converting from SMPTE-240M (above) with colorimetric rendering intent. They are close to Lindbloom's values but not exact; the error (±2 out of 255) is typical for 24-bit color file gamut mapping. If your monitor is well calibrated, this chart should appear nearly identical to the physical chart viewed under appropriate lighting (except  perhaps for the cyan patch, third row, right, which is outside the sRGB gamut). Simulated GretagMacbeth ColorChecker sRGB color space

Back to Implementation part 1: Setup, working color space, profile anatomy
Color management and color science: Introduction
Implementation part 2: Monitor profiling, workflow details
Obtaining profiles and building them with MonacoEZcolor | Evaluating printer color and ICC profiles


Images and text copyright © 2000-2014 by Norman Koren.
Norman Koren lives in Boulder, Colorado, founded Imatest LLC in 2004, previously worked on magnetic recording technology. He has been involved with photography since 1964.