Miscellaneous / Blog / 20060921
Here is another tip on getting the most out of LCD display calibration.
Adjust The In-Display Settings First
Most LCD displays have built in adjustible settings for color temp, brightness, contrast and even gamma. Getting these settings correct to maximize the number of tones the LCD produces can have a noted impact on the quality of color calibration.
LCD displays have a limited number of actual tones they can produce. The problem is that some LCD displays, in order to simulate traditional CRT and TV like adjustments, mangle the video signal such that 2 or more different video signal tones get mapped to the same tone on the LCD display. This limits the total number of tones that the LCD can display and results in poor quality.
There is a way to check this however. Right click and save the GIFs (four gradients) below. Then load these GIFs in a NON-color managed application (this is very important) such as ImageReady. Then zoom in to about 1600%. Scroll around and look at all sections of the gradient zoomed in. Each pixel column of the gradient is a different shade. If the LCD display is showing all 256 video signal tones, then each 1 pixel column of the gradient should show a slightly different tone. Checking the tones in the darks and lights is tricky. It is best to do this at night in a room with no outside lighting. Sometimes looking at the screen from an extreme angle will aid in checking the dark and light tones.
One method to adjust the LCD display settings to maximize the number of tones produced is to change the display settings while looking at the dark section of the gradient at 1600% zoom. Below is an example of how to do this.
- Start with Brightness at 0, Contrast at maximum, Gamma (if supported) at the default setting, and the Red, Green, and Blue color temp controls at the maximum.
- Bring the Brightness up until the desired overall brightness is found and, when looking at the display at an extreme angle, all tones in the darks are visible.
- Check for any clipping in the whites, if clipping is found then go back and tweek the Contrast.
- Also check all the Gamma settings (if supported). For example on the Samsung 910T, all other gamma settings but setting 1 causes loss of tones in the darks.
Depending on the LCD display and color calibration software, there are two methods for doing white point. The first is to let the calibration software adjust the profile to get to the proper white point. Sometimes this does not work. If that is the case then go in and adjust the RGB levels in the monitor's color temperature controls until the proper white point is found. With some calibration software this can actively be done while measuring the white point to make this a quick process.
Try Both the DVI Cable and the VGA Cable
Given that certain LCD displays can only display a set number of tones, sometimes it is better to use the VGA cable, because in the analog to digital conversion, the signal will dither on and off between the tones the LCD can actualy produce, simulating more tones. Using the DVI cable provides the LCD with a digital signal, so this temporal dithering does not happen.