Video Advice by Anthony D. Coppedge Contributing Writer July 20, 2008

CHURCH
“…I've gathered the kindergarten fact that the more lumens you have.... the brighter the projector is.”

Anthony
"The more lumens you have, the brighter the projector." Well, almost.

Here’s your second fact: In terms of measured lumen (how “bright”), yes, the more lumen, the more luminous (intensity of light output) the projector. However, brightness is perceived by the mind.

Our eyes do not respond in a linear fashion to increased light output. For example, if light output increases by a factor of 10, our eyes do not perceive a ten-fold increase in brightness. In fact the human eye senses changes in light output on a logarithmic scale, which allows our eyes to be sensitive over an extremely wide range of light levels. If you double the number of lumen, then the subjective perception will be that the "whites" get 25% brighter.

A simple demonstration of this is a darkened room with only a candle. You can see, but barely. Yet your eyes can adjust to a bright summer day outdoors just as easily. If our eyes responded linearly, we would either be able to see in darkened conditions or in bright conditions.

Let’s use an example of two projectors, based on the American National Standards Institute’s (ANSI) facts:

PROJECTOR 1 - with 1000 lumen and a contrast ratio of 400:1 (ANSI);
PROJECTOR 2 - with 1300 lumen and a contrast ratio of 150:1 (ANSI).

PROJECTOR 1 with only 1000 lumen will appear 'brighter' (to your eyes) than PROJECTOR 2 with 1300 lumen. To understand this, read on.

Since a video projector cannot project "black" light, control over the ambient (room) light is critical to attain an acceptable contrast ratio (white-to-black ratio). In reality, contrast ratio performance and screen dynamics are just as important as light output when it comes to displaying satisfactory images. So when looking at the projectors, the ANSI (not On/Off) contrast ratio can be very important.

Therefore, a projector with a higher ANSI contrast ratio will look brighter than a similarly ‘bright’ projector with less contrast ratio.

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