Why you should care about the contrast ratio
Contrast ratio is a term used to measure the difference between the maximum and minimum brightness of a screen. It is the difference between the whitest possible white and the darkest possible black. It is measured by displaying a black and white checkerboard pattern like the one below and comparing the values.
Because it is a ratio, the contrast ratio of a screen is represented as a number such as 1000:1. When a display has a contrast ratio of 1000:1, it means that a full-field white image is 1000 times brighter than a black. The larger the number, the better the screen is able to produce a natural-looking image.
The contrast ratio of a display is highly dependent on the underlying technology. OLED displays have a very marketable “infinite” contrast ratio, while the best-in-class LCDs from the likes of Samsung are over 7000:1. Contrast ratio is considered one of the most important aspects of image quality, so aim for a higher number if you can.
You can use a website like RTINGs to compare the contrast ratio of TVs and the contrast ratio of computer monitors.
A higher contrast ratio is better
The contrast ratio usually says a lot about the black values of a screen. How dark a screen can become ultimately depends on the type of screen.
LED-lit LCD televisions and monitors must shine a bright light through the thin-film transistor (TFT) layer of a screen to produce an image. When displaying black, the display does its best to exclude this light as much as possible. With older LCD technology, this often results in poor black levels. Blacks look like faded grays, or they can have areas of the screen that light passes through more easily, resulting in poor uniformity.
Compare this to self-emitting display technologies such as OLED, which achieve a theoretically “infinite” contrast ratio. Since the pixels can be turned off completely, the screen can display pure black in addition to bright white. This is what makes OLED displays so desirable, although they are not without their own drawbacks.
LCD isn’t a complete failure in this department, with newer mini-LED displays providing algorithm-driven dimming of the backlight. This allows LCD technology to get much closer to the inky black of an OLED by varying the light levels across the surface of the screen. Unfortunately, these screens still suffer from issues such as ghosting and black crush.
Buy a new television?
A display with a higher contrast ratio usually performs better in a dark room, while displays with lower ratios are usually optimized for brightness. Depending on where you watch TV and what you watch on it, a high-end OLED with an infinite contrast ratio can be a huge waste of money, while an LCD will do the job just fine.
Read more about buying the perfect TV for your situation and budget.