Monitor Settings

Monitor types:

CRT: Cathode Ray Tube
LCD: Liquid Crystal Display
TFT: Thin Film Transistor
TV : Television


Monitor Brightness Scale

Adjust the brightness of your monitor so that white appears white, black appears black and also the dark part of the colour bars can be distinguished.

Aspect Ratio

This test is only for CRT monitors. TFT/LCD displays have a fixed aspect ratio. Download the full screen test image that matches your monitor's resolution. Display it with a full screen image viewer or set it as desktop background. Don't resize the image!. Adjust the width and height of your monitor so that the circle has exactly the same width and height. Now your pixels are square.


This test is also only for CRT monitors. TFT/LCD displays have no disortion. Use the full screen test image from the previous step. Compare the white grid against a ruler. It should consist of straight horizontal and vertical bars with no pincushon or barrel disortion. Adjust your monitor disortion settings until the grid appears correctly.


Resolution Test Pattern

The image above shows three different pattern of 50% grey and one pixel resolution:

Gamma Correction

RGB Gamma Correction

The gamma value tells the monitor how much voltage is required to display a certain gray level when 0=black and 1=white. This correction of the gamma value is important for images on the World Wide Web to guarantee that your images are shown properly on different types of monitor and operating systems. If the gamma value of monitors differ, the same image does look either too bright or too dark on different monitors.

The gamma depends on display hardware (TFT, LCD, CRT, projector, TV) and the default gamma correction depends on graphics card driver or operating system. Most SUN and IBM computers have no hardware gamma correction and an overall gamma value of about 2.2-2.5, while most SGI and Macintosh computers have 1.8 because this more like the dot gain on a printer. On most flat screens (TFT, LCD) the gamma value even depends on the viewing angle.

Gamma correction is computed with this simple formula:

Intensity = Voltage gamma

Example: With a gamma value of 2.2 you have use a voltage of 0.73 (73%) to get an intensity of 0.5 (50%). With a gamma value of 1 the relationship is linear.

Determine Current Gamma Value

With the test pattern shown above it is easy to determine the current gamma value for each base colour (red, green, blue) and white. Just follow these steps:

  1. Darken your room.
  2. Set your monitors contrast to maximum.
  3. Adjust brightness so that black appears black.
  4. Defocus your eyes or stand stand back from your screen that your eyes can't resolve the checkboard pattern of the inner box.
  5. Choose the square where the inner box appears with the same brightness than the surrounding colour.
  6. The number above is the current gamma value of your screen.

Adjust Gamma Correction

When creating images for web sites I recommend gamma=2.0 because this is the average of the most commen display types. The methods of adjusting gamma depend on the system you use. I just can give a few advices.

GNU/Linux Use the command
xgamma -rgamma r.r -ggamma g.g -bgamma b.b
to determine the gamma correction and then add the line
Gamma r.r g.g b.b
to the Monitor section in your X server configuration file (/etc/X11/XF86Config).
MacOS X System Preferences > Monitors > Colors > Calibrate
Then follow the instructions of the assistant. Adobe Photoshop offers a separate tool for adjusting monitor and colour profile.
Windoze Seems to be no OS native gamma support. Look into your video card driver applicaton or use Adobe Gamma from Adobe Photoshop.