Home audio & video: Contrast Ratio

Quick answer at a high level

These previous posts are great for links but some quick guidlines on "dynamic contrast ratios" (which is all the Asus smart contrast is I think).

Old CRT monitors worked by firing light from the back of the tube onto the back of the screen. That light could be green, red, blue or a mixture thereof.

New LCD montiors work differently. Each pixel on the screen is basically a small set of windows, one green, one red and one blue. These windows can be opened all the way or partially. The mixture of these colored "windows" create colors. The problem with this is that the LCD panel itself doesn't generate any light.

In order for you to be able to see anything, these LCD screens have what essentially amounts to a big light bulb behind them, that shines through those little windows and creates the picture.

This creates an issue where even when all the colored windows in each pixel are closed (which should be black) some light still leaks around the edges of the windows from the light behind, resulting a in grey look to black parts of the picture.

Contrast ratio is simply a measurement of how black an all black screen actually is as a ratio of how bright the all white screen is. That is true contrast ratio, and the one that should be condered when purchasing.

What the LCD panels makers do is say "we know that in most cases the times that really black blacks are important are during dark scenes". Therefore the monitor measures how dark the scene is in general, and actually dim the light behind those windows, so that less light leaks through "closed doors" during a darker scene, making a darker picture.

Therefore this dynamic ratio is measured as: all windows closed and the back light off (or almost off, depends on who is measuring) all the way up to light fully on, doors all open (white).

The two major problems with dynamic contrast ratios is they really only tell you how dark the monitor could be in a totally dark scene, and there is no standard of measurement, so two manufacturers releasing exactly the same hardware, could come out with different dynamic ratios.

This turned out longer than I had anticiapted, but I hope it helps some!