Monitor Calibration - Step by Step

Profile Prism
Procedure for calibrating a monitor

Background

Monitor Profiling Versus Monitor Calibration:

There are two ways to improve the accuracy of images displayed on your monitor.

Monitor calibration
Profile Prism provides a monitor calibration only. Calibrating a monitor involves adjustment of the monitor's contrast, brightness, and RGB gains (red, green, and blue gamma) so that the monitor responds in a linear fashion with respect to gamma 2.2, the gamma used by Windows systems. This operation ensures good "baseline" monitor performance by minimizing color casts. Monitor calibration tools are based on manual/visual input from the user and usually consist of two major phases: (1) adjustment of the monitor's [hardware] contrast, brightness, and color temperature and (2) visual adjustment of the red, green, and blue gains through software.

The first phase of adjusting the contrast, brightness, and color temperature requires adjustment of the monitor via the control panel on the front of the monitor. The second phase of adjusting RGB gains is accomplished via software controls. Once phase 2 is complete, the RGB gains are loaded into the Windows startup so that the gains are adjusted each time the system boots. It is important to understand that monitor calibration is a separate step from profiling and does not require/involve any ICC profiles.

Remember that calibration is only used to ensure that a monitor is adjusted properly and operating to a known baseline. Once monitor calibration is complete, most Windows monitors should conform reasonably well to the sRGB color space. sRGB is a good middle ground for an average monitor attached to a Windows system, so after calibration has been performed, you should use "sRGB Color Space Profile" as the ICC profile for your monitor.

Note that some other visual calibration tools produce an ICC profile as part of the calibration process. The profile is based on user selection of tristimulus values (phosphor type for a certain monitor type/brand) and system gamma. This profile is usually loaded by the calibration tool into the display properties "color management" tab to be used by imaging software. Windows as a system does not/cannot use the profile that is listed under your display properties; it simply identifies the profile that is associated with your monitor so that imaging applications can look up the association and use the proper profile. Profile Prism does not produce a profile as a result of the calibration process, and the use of sRGB is recommended instead. ICC profiles generated by visual calibration tools are based entirely on guesswork by the user (as to the phosphor type/color response) and therefore are often worse than simply using the "sRGB Color Space Profile" for your monitor. The only way to obtain an actual monitor ICC profile that is guaranteed to be more accurate than simply using sRGB is to profile a monitor with a colorimeter (see below).

Monitor profiling: Profiling a monitor involves using a colorimeter (a small device that attaches to the screen) to take actual measurements of the monitor's color performance. This is by far the most accurate method of monitor color management, but is also the most costly because it requires the purchase of hardware to take measurements. In addition to being able to produce a better overall monitor calibration, colorimeter-based monitor profiling tools are also able to measure the monitor's phosphor/color response so that an accurate ICC profile can be generated. The basic process for monitor profiling is similar to monitor calibration except that the second phase of the process is modified such that actual measurements are taken in order to generate a usable/accurate ICC profile for the monitor. Profile Prism does not currently support true colorimeter-based profiling.

Step by Step Procedures

Calibrating a Monitor with Profile Prism:

Click "Edit", "Calibrate Monitor" from Profile Prism's main window.

Step 1 requests that the monitor's color temperature be set to 6500K. Most monitors have a selection called "Color Temp", "White Point", "Color Adjust", etc. that allows selection of color temperatures like 6500, 9300, etc. If you are unable to make the selection of 6500K, you may need to skip this step as your monitor may not offer this control. Click "OK" when finished with this step.

Step 2 relates to adjusting the monitor's contrast and brightness controls, and shows a black square with a dark gray square inside. Start by setting both the contrast and brightness to maximum using the controls on the front of the monitor. Then reduce brightness until the dark gray square inside the black square is barely detectable/visible. Make the adjustment in normal room lighting. You should not need to "stare" at the square to be able to detect the dark gray inner square; just set brightness so that at a quick glance, the inner dark gray square is visible.

Step 3 involves adjusting the RGB gain (monitor gamma). Start by sitting a sufficient distance from the monitor and/or squinting so that the line patterns in the colored outer boxes are not visible. Slide the red slider left/right until the inner red box appears to be the same brightness as the outer border. Pay attention to both red "swatches" (top/bottom) and try to achieve the best match for both. If it is not possible to achieve equal brightness for the inner square/outer border for both red boxes at the same time, do your best to make the best compromise between the two. Repeat this process for the green and red boxes using the sliders under those test swatches. When you have completed all three, look at the two gray scales between the red/green and green/blue boxes. Do they look gray? If not, you can make minor adjustments to remove color casts. The intent is to achieve the most equal inner/border brightness on the red, green, and blue boxes while not introducing color casts into the gray scales. Again, make the best compromise. Note that you can click just to the left/right of the slider to move the slider one point left/right. Click "OK" when done.

At this point the process is complete and your monitor is calibrated. Profile Prism adds a small, non-resident program to your Windows startup sequence called "ppgamma.exe". This "ppgamma" program simply loads the RGB gains (monitor gamma) each time you boot your machine. There is no need to reboot since the calibration is already in effect.

The Monitor is Calibrated. Now What?

Profile Prism's monitor calibration is similar to that performed by other visual calibration tools on the market. It simply allows you to adjust your monitor so that it performs "like it should". Since this step can be interpreted as a simple "monitor tune-up", it does not involve ICC profiles. As noted above, some other visual calibration tools allow selection of monitor phosphor type, tristimulus values, or monitor brand and actually save an ICC profile as a result of these selections. Unfortunately, it is impossible to accurately "predict" color response based on any of these selections because color response varies across phosphor types, brands, models, and even the age and physical condition of the monitor. As a result, the ICC profiles produced by visual calibration tools cannot be relied upon for accurate color management and often lead to a result that is worse than just using the Windows/web sRGB standard. For this reason, we recommend simply using sRGB as the color space for your monitor after performing the monitor calibration.

Once you have calibrated your monitor, simply select "sRGB Color Space Profile" as your monitor profile in your imaging software. This profile should be located in your Windows color folder. If not, it is also provided in your Profile Prism installation folder (normally \program files\prism). The methods for "activating" sRGB as your monitor profile are:

Activating sRGB as your monitor profile in Qimage:
Open Qimage and click "Monitor ICC" on the lower right of the main window. When the color management dialog opens, check the box for "Monitor" and then click the "..." browse button next to the monitor profile edit box in that group. When the profile selection window opens, click "Utility Profiles" on the bottom right and then select "sRGB". Click "OK" to accept the changes. When you return to Qimage's main window, "Monitor ICC" should now read "sRGB".

Activating sRGB as your monitor profile in Windows and photo editors:
Many photo editors look up the association for monitor profile in the display properties and use whatever profile is listed there. For this reason, if you use ICC aware photo editing software (other than Qimage), you should activate sRGB as the monitor profile at the Windows level. To do this, right click on your desktop background in Windows. Select "Properties", and the display properties should appear. Click the "Settings" tab and then click the "Advanced" button. Next, click the "Color Management" tab. If "sRGB Color Space Profile" is already listed under "Color profiles currently associated with this device", simply select that profile in the list and click "Set as Default". If not listed, click "Add", select "sRGB Color Space Profile.icm" and once added, click "Set as Default". Remember that you can select "sRGB.icm" from \program files\prism if you are unable to locate "sRGB Color Space Profile.icm" in the standard Windows color folder.

What about double profiling?
You may be wondering about the possibility of double profiling if you activate sRGB as your monitor profile on your display properties and you've also activated it as "Monitor ICC" in Qimage. The simple answer is, don't worry about double profiling. Windows does not/cannot utilize a profile at the system level, so associating sRGB with your monitor under the display properties will have absolutely no effect on Windows itself. Associating sRGB as your monitor profile under the Windows display properties serves as nothing more than a placeholder. It is not used in any way by the Windows system itself! In other words, if you use both Qimage and other ICC aware photo editors, you should activate sRGB as your monitor profile both in Qimage and under your display properties as well.

Removing the Profile Prism gamma loader (ppgamma) from your Windows Startup:
If you run into any startup problems or would like to remove the Profile Prism gamma loader utility from your Windows start sequence, simply start Profile Prism and click "Edit", "Disable Startup Monitor Calibration". The gamma loader program called "ppgamma" will then be removed from your Windows startup.

If "Disable Startup Monitor Calibration" is grayed out in the menu, you know that the gamma loader is not currently in your Windows startup sequence. Conversely, if "Disable Startup Monitor Calibration" is enabled, your Windows startup sequence currently contains the gamma loader. If you disable the gamma loader and would like to reenable the option at a later time, simply select "Edit", "Calibrate Monitor" and run the monitor calibration routine again. Once you finish the calibration routine, the Profile Prism gamma loader will automatically be added to your Windows start sequence. Note that "ppgamma" will not appear in your "Startup" folder; it is loaded with other background utilities in your Windows boot sequence.