What Pixels Are and What They Mean for TV Viewing

The dots that make up your TV picture

When you watch your favorite program or movie on a TV or video projector, you see what appears to be a series of complete images, like a photograph or film. However, appearances are deceiving. If you get your eyes close to a TV or projection screen, you'll see it is made up of little dots that are lined up in horizontal and vertical rows across and up and down the screen surface.

Pixel Display in screen
kisina/Getty Images

The Pixel Defined

The dots on a TV, video projection screen, PC monitor, laptop, or even tablet and smartphone screens, are referred to as pixels.

A pixel is defined as a picture element. Each pixel contains red, green, and blue color information (referred to as subpixels). The following illustration shows a close-up of subpixels.

Illustration of What LCD TV Pixels Look Like
Wikimedia Commons / Public Domain

Pixels and Resolution

The number of pixels that can be displayed on a screen surface determines the resolution of the displayed images. To display a specific screen resolution, a predetermined number of pixels has to run across the screen horizontally and up and down the screen vertically, arranged in rows and columns.

To determine the total number of pixels covering the entire screen surface, you multiply the number of horizontal pixels in one row with the number of vertical pixels in one column. This total is referred to as pixel density.

Here are some examples of pixel density for commonly displayed resolutions in today's TVs (LCD, Plasma, OLED) and video projectors (LCD, DLP):

Stated Resolution Horizontal Pixel Count Vertical Pixel Count Pixel Density (Total Pixel Count Displayed)
480i/p 720 480 345,600
720p 1,280 720 921,600
768p 1,366 768 1,049,088
1080i/p 1,920 1,080 2,073,600
4K (Consumer Standard) 3,840 2,160 8,294,400
4K (Cinema Standard) 4,096 2,160 8,847,360
8K 7,680 4,320 33,177,600

Pixel Density and Screen Size

In addition to pixel density (resolution), there is another factor to take into consideration: the size of the screen displaying the pixels.

Regardless of screen size, the horizontal/vertical pixel count and pixel density don't change for a specific resolution. If you have a 1080p TV, there are always 1,920 pixels running across the screen horizontally, per row, and 1,080 pixels running up and down the screen vertically, per column. This results in a pixel density of about 2.1 million.

A 32-inch TV that displays 1080p resolution has the same number of pixels as a 55-inch 1080p TV. The same thing applies to video projectors. A 1080p video projector will display the same number of pixels on an 80 or 200-inch screen.

Pixels per Inch

Even though the number of pixels stays constant for a specific pixel density across all screen sizes, what does change is the number of pixels-per-inch.

As the screen size gets larger, the individually displayed pixels have to be larger, or the space between the pixels increased, in order to fill the screen with the correct number of pixels for a specific resolution. You can calculate the number of pixels per inch for specific resolution/screen size relationships.

TVs vs Video Projectors

With video projectors, the displayed pixels per inch for a specific projector can vary depending on the size screen used. Unlike TVs that have static screen sizes (a 50-inch TV is always a 50-inch TV), video projectors can display images in a wide variety of screen sizes, depending on the projector's lens design and the distance the projector is placed from a screen or wall.

With 4K projectors, there are different methods on how images are displayed on a screen that also affects the screen size, pixel density, and pixels per inch relationship.

TV and Video Projector Images – More Than Just Pixels

Although pixels are the foundation of how a TV image is put together, there are other things that are required to see good quality TV or video projector images. These include brightness, contrast, color, tint, color temperature, and other settings.

Just because a TV or projected image has a lot of pixels, doesn't automatically mean you'll see the best possible image.