- 100% Contrast
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.
When it matters
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.
Our ‘Black’ test represents the measured luminance of black on the screen. This tells us how deep black is going to be, and is the more important measurement of the two that we do (the other being the measurement of the luminance of white). If you want nighttime scenes to look good and dark, deep blacks are important.
To measure the luminance of black, we use a black and white checkboard 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.
We use the checkboard pattern instead of a full black frame in order to prevent the TV from 'cheating'. Most TVs will turn down the backlight when a full or almost full black frame is shown. A checkboard pattern prevents this kind of trick, unless the TV has well-implemented full-array local dimming.
We do also try the local dimming feature to see if it is able to improve the blacks on our pattern. Unfortunately, no TV has been able to do so while still keeping the same white luminance.
Our ‘White’ test represents the measured luminance of white on the screen. This matters for the appearance of white objects, like clouds or snow, and also sets the limit for all other colors on the screen, since everything else will be less bright than pure white. Because we calibrate for a dark room, and all TVs are able to get bright enough to look fine in that sort of environment, this test isn’t so important. However, doing this is a necessary part of the overall contrast evaluation, which is why we perform it.
This isn’t really much of a ‘test,’ as we use the same target of 100 cd/m2 light emittance for white on all TVs, and most TVs can be set to right around that level. We use our luminance meter to measure luminance of the screen, and then find the right lighting setting on the TV to achieve our target.
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.
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.
OLED vs LED
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.’
How to get the best results
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.
Related settings & other notes
- Contrast: Adjusting this will let you affect how much contrast the TV has. We list a recommended setting with all of our reviews, but it's almost always fine to just set this to the maximum. On rare occasion, gamma might be affected, leading to a loss of detail in highlights.
- Local dimming: Dims the backlight behind darker portions of the screen. Does deepen contrast, and worth using when implemented well. Can introduce issues like light blooming off of light objects within dark areas, and when done especially poorly, can dim the entire image. We discuss local dimming in more detail here.
- Dynamic contrast: Uses software to process the blacks and make them darker. Unfortunately, this removes detail from the image. Not worth using.
- Full/limited RGB: Full RGB may offer slightly more detail in blacks and shadows, but it’s not a big difference when compared with limited RGB. Just make sure that both your TV and your source device use matching RGB settings.
- Gamma: Gamma does not control the depth of black, but it does control the amount of detail you will see in dark portions of an image. If you find it difficult to make out detail in dark images, consider making a slight adjustment to the gamma. We discuss gamma in more detail here.
- Highlight brightening: Makes highlights in images extra bright, which will affect how contrast looks. Worth using with HDR media, but not really useful for most video.
- Backlight/OLED light settings do not affect contrast, and so you should set them to whatever looks best in your viewing space. With LED TVs, both white and black will become about equally brighter or dimmer when the backlight is adjusted, preserving the ratio of light to dark. With OLED, blacks will remain perfectly black, and only other colors will become brighter.
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.
There are many things that 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.