The contrast ratio is the ratio between the luminance of the brightest white and the darkest black that a TV can produce. Larger contrast ratios work out to deeper blacks, which make a big difference to overall picture quality. It’s of particular importance for dark scenes in movies and TV shows.
To test contrast, we measure the luminance of both white and black, and then calculate the ratio between the two. Luminance is a metric to measure the amount of light (or intensity) present on a surface and is expressed in cd/m2. For TVs, the brighter the light of the screen is, the higher the luminance will be.
The contrast ratio is the best indicator of how good a picture can look, as an image will generally look better if the blacks are really dark and the whites are really bright - if you are watching a dark movie, you don't want the image to look like a washed-out gray instead of being black. Because TVs can mostly achieve the same brightness of white, the contrast ratio really represents how dark black will be, and a higher number will mean darker blacks.
Keep in mind that having the deep, dark blacks you get from good contrast is mostly a benefit when you watch TV in a dark room. In brighter rooms, reflected ambient light will reduce the perceivable difference you might get with darker blacks, and so higher contrasts won’t look so different. Good contrast is also more noticeable with dark, shadowy scenes - it probably won’t make a big difference while watching something like football, or a bright and colorful cartoon.
On TVs, contrast is the ratio between white and black and is really the only one of these tests that should be looked at. A higher contrast ratio means deeper blacks and better picture for dark scenes viewed in a dark room.
The 'Native contrast' represent the contrast ratio of the panel used to build the TV and is measured without any image processing added or features design to accentuate the contrast ratio like local dimming.
To measure the luminance of the black and the white, we use a black and white checkerboard pattern. We calibrate the television to have a white luminance of about 100 cd/m2 and then we measure the luminance of a black square on the same picture.
Once we have measured the black and the white, we are able to calculate what the contrast ratio is. To get this number, we divide the white luminance by the black luminance.
Because it is a ratio, there is no unit for contrast. Instead, the norm is to express the number as ‘X:1,’ with ‘X’ being how many times brighter white is than black. For example, a 2,000,000:1 contrast ratio would mean that the television emits white that is two million times brighter than its black. The higher the contrast ratio, the deeper the blacks, and the better the picture will look.
The 'Contrast with local dimming' is similar to the 'Native contrast' but calculated with the local dimming turned on and set to high. This is also measured on a checkerboard pattern, with the same method used for the native contrast.
OLED sets have much better blacks than LED TVs do. This is because, with OLED panels, there is no backlight; the pixels emit light themselves, so a black pixel is just left off, and remains perfectly dark. That’s why OLED TVs tend to be listed as having ‘infinite contrast’ – you can’t divide the white luminance by a black luminance measurement of ‘0.’
As a first step, try using the calibration settings we recommend (provided we have reviewed your TV). This will get good, basic contrast - meaning no additional contrast-enhancing settings - and with no loss of detail in dark portions of the image. You can find links to those at the top of each review. In particular, you should copy the ‘Brightness’ and ‘Contrast’ settings.
Most TVs also have a few other settings that affect contrast. We listed a few below, along with our thoughts on whether or not they should be used.
A TV’s contrast ratio indicates the depth of blacks – a higher contrast ratio means deeper blacks – with higher contrast meaning better picture. It’s a very important part of picture quality, so if you want something that looks really good (particularly in a dark room), be sure to get a TV that has good contrast. When testing for contrast, we measure the luminance of black and of white and then divide white by black to get the contrast ratio number.
Many things can be done to improve contrast. As a good first step, look to our recommended picture settings (listed with every review), as those can help you get a good baseline. From there, you can enable or disable a few different settings that might help deepen blacks. Just remember that some of those settings will have other consequences for picture quality.