Wednesday, December 17, 2008

Calibrating Monitors with the Eye-One LT
including dual monitors and dual LUTs

I've spent the last four years staring at two monitors side by side that do not have matching colors. After a while, a minor irritant turned into a major irritant, and I bought the X-Rite Eye-One LT (aka the i1) to fix the problem.

As numerous others have noticed, the documentation leaves a great deal to be desired, so here is my addendum.

1. Don't bother installing from the CD. It's all out of date. Install the latest versions of the software from:

The only software required for calibration is i1Match, which is Vista-compatible as of v3.6.2. (You do not need to install the download labeled 32 & 64-Bit Drivers for Win2000, XP, and Vista. The drivers are included with i1Match)

2. Install the software before you plug in the USB cord. The manual is wrong when it says to do it the other way around.

3. Understand what your monitor is capable of. For the purposes of calibration, there are three classes of LCD monitors:

  • Monitors that do not allow you to adjust the contrast or whitepoint. My 5-year old Samsung 191T fell into this category. Eye-One works with these monitors, but the results are suboptimal. In general, it is almost impossible to calibrate these older monitors to be the same as other monitors.
  • Monitors that allow you to manually adjust the contrast, whitepoint, or RGB values. i1 walks you through making adjustments. The quality of the result depends on the number of adjustments available on the monitor.
  • Newer monitors where Eye-One is able to automatically control the monitor to set contrast, RGB and whitepoint. Such monitors are the easiest to calibrate and will have the highest level of success. Note that Eye-One only has built-in support for automatically controlling a small number of monitors. For other monitors, you'll need to manually make the adjustments.

4. Ambient light matters. The ambient light in your room has a significant impact on the result. Make sure you calibrate your monitor in the light where it's normally used. Don't do what I did and calibrate your monitor at night when the room is lit up with incandescent bulbs. The result is not satisfactory. (Note that the i1Match software actually warned me about this when I turned on "measure ambient light". The measurement bars shows that the light in my room was inappropriate for successful color correction.)

If you have Vista, you may also run into the problem of your color correction settings being lost every few minutes. Install Vista Service Pack 1.

5. Run the calibration. This is generally fairly painless. Make sure you read the help panel on the right in i1Match - it has useful information. Make sure you do the Contrast adjustment, if i1Match asks you to.

If you are calibrating an LCD monitor, you should use the counterweight instead of the suction cups built into the sensor. I found that the suction cups wouldn't stick to the matte screen of my LCD monitor.

6. Understand LUTs. The LUT, or "LookUp Table," is a feature of your video card that automatically performs color correction at all times. Without a video LUT, color correction only works in software like Photoshop and PaintShop Pro that can perform software-based color correction. Virtually all video cards made in recent years contain a hardware LUT.

You can verify that your video card has LUT support by downloading the LUT Tester.

When you run color calibration software such as i1Match, the result is an ICC file. ICC stands for Internation Color Consortium. The file contains information on how RGB values need to be adjusted to display properly on your monitor.

Here's the annoying part. Windows, even Windows Vista, does not understand how to load the hardware LUT with the ICC file. So Windows has all of the infrastructure to track ICC profiles for each monitor, but Windows doesn't actually do anything with that information!

The solution is software that loads the LUT when Windows starts. Such software reads the ICC profile for each monitor and loads the appropriate LUT. The most common example is Adobe Gamma Loader, but the Eye-One includes the Logo Calibration Loader, which should always be used to load the LUTs.

7. Dual monitors and Dual LUTs. This one is the 900-pound gorilla. The problem with dual monitors is that you need dual LUTs. Every monitor requires a unique calibration, even two monitors that are the identical model. Many video cards today have connections for two monitors. In order to show the correct colors in both of them, each must be calibrated separately AND your video card(s) must have one LUT for each monitor. Most low-end video cards (and most pre-2006 video cards) only have a single LUT, which means that either you need a second video card for your second monitor or you need to upgrade to a card with dual outputs and dual LUTs.

It can be tricky to determine if your system will be able to calibrate two monitors. There are several variables:

  • Operating system: If you are running Windows Vista SP1, then the OS includes the required support. If you are running Windows XP, then you need to install extra software.
  • Eye-One software. The i1Display 2 software apparently has built-in support for multiple monitors. The i1Display LT software does not support multiple monitors, but see my workaround below.
  • Dual LUTs. To determine whether your video card has dual LUTs, run through the calibration on the primary monitor. On the final screen, use the Calibration On/Off button to see how calibration affects your monitor. If you have dual LUTs, then only the primary monitor will be affected by the Calibration On/Off button. If you only have a single LUT, then both monitors will be affected.

I have verified that the Logo Calibration Loader supports multiple LUTs. It is intelligent enough to read the ICC profile for each monitor and set the appropriate LUT.

My system has an nVidia 7950GT video card. I was very happy to discover that this card has dual LUTs.

8. Remove conflicting software. When you install i1Match, your Startup group is updated to include the Logo Calibration Loader. This sofware updates the LUT(s)in your video card. Unfortunately, there are several other applications that try to do the same thing and must be removed. The most common is the Adobe Gamma Loader, which is installed with PhotoShop.

9 Advanced users. If you want to know more about what your monitor can do, download and the free sofware HCFR. Although this software will not create or manipulate ICC profiles, it will give you copious information about ambient light, your monitor's color space, and more. Just be prepared to spend some time figuring how it works. You'll also need to copy EyeOne.dll into HCFR's installation directory. Make sure you enable Eye-One support in HCFR.

10 Finding your ICC profiles in Vista. The ICC profiles are managed by Windows. To view them in Vista, go to Control Panel | Color Management. Note that this information is maintained on a per-monitor basis and you can switch between monitors using the droplist at the top of the window. Important! If you change the default ICC profile for a monitor, you'll notice that your screen colors do not change. You must run the Logo Calibration Loader to update your LUTs after you change the ICC profile. You can run this Loader from the Start menu or from C:\Program Files\GretagMacbeth\i1\Eye-One Match 3\CalibrationLoader\CalibrationLoader.exe.

11 Calibrating your second monitor with Eye-One LT. The cheaper LT version of Eye-One does not include built-in support for multiple monitors, but the workaround is easy. (This is for Vista, I haven't tested this in XP.) This process assumes that you have already completed the calibration for your primary monitor and that you've verified that you have dual LUTs. Here is how to calibrate your second monitor:
  • Open Control Panel
  • Open Personalization
  • Open Display Settings
  • Left-click the big #2.
  • Check the box labeled "This is my main monitor."
  • Left-click the big #1.
  • Uncheck the box labeled "Extend the desktop onto this monitor."
  • Click Apply
  • Your primary monitor is now disabled. You should be able to run i1Match and calibrate the second monitor without difficulty. The ICC profile for the second monitor will be set to the new ICC profile and the ICC profile for the first monitor should be unchanged.
  • Reenable your primary monitor by reversing the steps above for the "big #1" and the "big #2."
  • Run the Logo Calibration Loader to reload the LUTs for both monitors. This step is required.

Other Thoughts

I'm quite happy with my Eye-One. It calibrated my desktop PC, my laptop, and my Mac. It's considered to be the best colorimeter on the market that's "affordable." (The Spyder hardware also appears to score well, but Amazon Reviews are littered with complaints about their software.)

Another alternative is the Huey, which is half the price of the Eye-One. However, the Huey cannot calibrate luminence, which is critical for calibrating today's excessively bright LCD monitors. Also, luminence calibration is required in dual monitor setups to make both monitors appear the same.

After final calibration, I was not able to get good results calibrating my Samsung 191T or 191T+. However, both of these monitors are over four years old, both have over 15,000 hours on their backlights, and neither has an adjustable whitepoint. So the poor results are to be expected. (Both monitors looked better after calibration than before calibration, so there was definite improvement.) On the other hand, my brand new HP 2475w ended up with near-perfect calibration. After creating the ICC profile and loading the LUTs with Eye-One, I switched to HCFR to graph the results and the results were excellent. Luminance was a perfect match to theoretical and RGB was corrected within 5% for all values.

[Update 2/25/2009] I tested the latest version of i1Match (3.6.2) under Windows 7 Beta and it worked correctly. The Logo Calibration Loader also worked. One small hiccup was that it couldn't find the position of the sensor, but I just told it to continue and it worked fine.

[Update 5/21/2009] I upgraded the T42/p from Win7 Beta to Win7 RC. I copied the color profile from the Beta to the RC, set it to be the default, and the screen magically updated - even though I didn't start Logo Calibration Loader. This means that, as of Windows 7, Windows finally includes support for automatically loading the LUTs based on the color profile. Great news! (This means that you can remove the the Logo Calibration Loader from your Startup group if you have Windows 7.) Note that I was not able to test dual monitors to see if Windows 7 could handle multiple LUTs.