Contrast in Monitors, OR What is Contrast Ratio
Answer by Solandri:
Contrast is a bit of a loaded term today.
It originally meant the ratio between the brightest white and the darkest black the screen can display.
LCD monitors are notorious for poor contrast because they have a hard time displaying black (entirely blocking all of the backlight). We went from about a million to 1 contrast ratio on CRTs, to a few hundred to one on LCDs. Nowadays, about 700:1 is typical. Below 500:1 is poor. Above 1000:1 is good. The highest I've seen is about 1800:1.
To confuse you, monitor makers came up with dynamic contrast. This is where in a dark scene, the monitor will lower its backlight brightness to make the scene darker. During a bright scene, the monitor will increase its backlight brightness to make the scene brighter. They report this as a dynamic contrast ratio, though less scrupulous manufacturers just call it contrast ratio to confuse you. It's typically about a million to 1. It's not true contrast ratio because you can't see the brightest white and darkest black at the same time. Any LCD contrast ratio you see advertised as more than 10,000:1 is dynamic contrast ratio, not contrast ratio.
Technological progress has made dynamic contrast ratio somewhat relevant. Some newer monitors can turn off individual backlights (they're strips or grids of individual LEDs). So if the image the monitor is displaying is dark in one corner, bright in another corner, the monitor will turn down the backlight in the dark corner, while turning up the backlight in the bright corner. This is limited to a few dozen LED backlights though, so can't give pixel-level resolution of dark/bright contrast. However, it can be somewhat effective in real-life scenes like movies or games.
OLED theoretically has infinite contrast ratio. OLED turns individual pixels on or off like CRTs did. There is no backlight which can bleed through. When an OLED display turns a pixel off, it emits no light, so the black is theoretically perfectly black. And unlike a CRT, the pixels which are lit are the only ones lit - there is no spillover to adjacent pixels. CRTs had that problem, making the pixel fuzzy, due to the electron beam spreading a bit as it traveled between the back to the front of the monitor. Since OLED's blacks are theoretically perfectly black, the contrast ratio is some number divided by zero, which is theoretically infinite.
High contrast ratio is most noticeable when you're using the monitor in a dark room. A low contrast ratio monitor will be noticeably brighter when displaying black. Likewise, if you're using the monitor in a bright room or in sunlight, the contrast ratio won't matter as much. The maximum brightness will be more important.
Answer by Solandri:
Contrast is a bit of a loaded term today.
It originally meant the ratio between the brightest white and the darkest black the screen can display.
LCD monitors are notorious for poor contrast because they have a hard time displaying black (entirely blocking all of the backlight). We went from about a million to 1 contrast ratio on CRTs, to a few hundred to one on LCDs. Nowadays, about 700:1 is typical. Below 500:1 is poor. Above 1000:1 is good. The highest I've seen is about 1800:1.
To confuse you, monitor makers came up with dynamic contrast. This is where in a dark scene, the monitor will lower its backlight brightness to make the scene darker. During a bright scene, the monitor will increase its backlight brightness to make the scene brighter. They report this as a dynamic contrast ratio, though less scrupulous manufacturers just call it contrast ratio to confuse you. It's typically about a million to 1. It's not true contrast ratio because you can't see the brightest white and darkest black at the same time. Any LCD contrast ratio you see advertised as more than 10,000:1 is dynamic contrast ratio, not contrast ratio.
Technological progress has made dynamic contrast ratio somewhat relevant. Some newer monitors can turn off individual backlights (they're strips or grids of individual LEDs). So if the image the monitor is displaying is dark in one corner, bright in another corner, the monitor will turn down the backlight in the dark corner, while turning up the backlight in the bright corner. This is limited to a few dozen LED backlights though, so can't give pixel-level resolution of dark/bright contrast. However, it can be somewhat effective in real-life scenes like movies or games.
OLED theoretically has infinite contrast ratio. OLED turns individual pixels on or off like CRTs did. There is no backlight which can bleed through. When an OLED display turns a pixel off, it emits no light, so the black is theoretically perfectly black. And unlike a CRT, the pixels which are lit are the only ones lit - there is no spillover to adjacent pixels. CRTs had that problem, making the pixel fuzzy, due to the electron beam spreading a bit as it traveled between the back to the front of the monitor. Since OLED's blacks are theoretically perfectly black, the contrast ratio is some number divided by zero, which is theoretically infinite.
High contrast ratio is most noticeable when you're using the monitor in a dark room. A low contrast ratio monitor will be noticeably brighter when displaying black. Likewise, if you're using the monitor in a bright room or in sunlight, the contrast ratio won't matter as much. The maximum brightness will be more important.
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