What Pixels Are and What They Mean for TV Viewing

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.

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.

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):

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.

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.

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.

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.