Video Projectors and Color Brightness

Your video projector may not be as bright as you think it is

When considering a video projector, probably the most apparent specification is the lumens number. Lumens is a measure of how much light a video projector can output.

However, just as with other specifications, be cautious with provided lumens numbers, as there is no official standard required. A stated Lumens rating used by one projector brand may not be the same as another brand.

On the other hand, if the lumens rating is in terms of ANSI lumens, that is an industry-standard that is consistent if comparing two brands that use ANSI as their reference.

White Light Output vs. Color Brightness

However, there is more to consider in terms of how much light a video projector can produce. When a manufacturer states a single lumens rating, it references how much White Light Output (WLO) or White Brightness the projector can produce, not the total light output considering color. For example, two projectors could have the same WLO rating, but the color light output (CLO), or Color Brightness, might be different.

Video Projector Color Brightness Comparison - DLP vs LCD
Video Projector Color Brightness Comparison - DLP vs LCD. Photo © Robert Silva - Licensed to About.com

Side-By-Side Comparison

To illustrate the difference, the above photo shows a side-by-side demonstration of color's effect on video projector lumens, or light, output. Both projectors in the image have the same White light output capability but differ in the amount of Color brightness that is present.

There is a difference in the Color Brightness of the two projectors because the projector on the left side uses a 1-chip DLP design (Optoma GT750E). In contrast, the projector on the right used a 3LCD design (Epson PowerLite Home Cinema 750HD). Both projectors have the same native display resolution (720p) and the same ANSI lumens WLO specification: 3,000. The stated contrast ratio for the Optoma is 3,000:1, and for the Epson is "up to" 5,000:1.

However, the projector on the right appears to have brighter, more vibrant colors and overall brightness than the projector on the left.

How Projector Technology Design Affects Color Brightness

3LCD design projector allows all of the white and color light to continuously pass through the lens, resulting in an equal amount of perceived White and Color Brightness. However, in a 1-Chip DLP design, light has to travel through a spinning color wheel divided into red, green, and blue segments.

With projectors that use the 1-chip DLP system, colors project sequentially (in other words, your eye is not receiving color information continuously), resulting in much lower color light output than the white light output. One-chip DLP projectors often compensate by adding a white segment to the color wheel to boost White Brightness, but the fact remains that the degree of Color Brightness is less than the White Brightness.

This difference is usually not stated by the manufacturer in their projector specifications. You most often see a single Lumens output specification, rather than one that lists two lumens specifications. One is for WLO (White Light Output) and another for CLO (Color Light Output), which provides a more accurate profile of how much Color Brightness you can perceive.

On the other hand, 3LCD Projectors employ a mirror/prism assembly (no moving color wheel) combined with a separate chip for each primary color (red, green, blue), so both white and color continuously reach your eye. This results in consistent White and Color Brightness.

As a direct result of the different technologies used, for the 1-chip DLP projector on the left to produce as much Color Brightness as the 3LCD projector on the right, it needs to have a much higher White Light Output capability. A 1-chip DLP projector would have to use a higher-wattage lamp and the resultant increase of power consumption.

The Direct Effect of Brightness

Referencing the photos shown, Color Brightness has a direct effect on what you see on the screen. This is important for typical home theater viewing, in rooms with uncontrolled ambient light, 3D viewing, or video projectors in educational or business settings with unknown light conditions.

Increased color brightness also increases the perception of details within the image, regardless of the display resolution. The overall contrast level is the only factor that can suffer when you increase color brightness. However, other video processing factors can affect this result.