Beyond ON/OFF & ANSI
ON/OFF contrast and ANSI contrast by no means tell you the whole picture as far as contrast and black levels performance is concerned. Why? Because neither ON/OFF nor ANSI in themselves directly describe what is the contrast and black levels performance of actual video content.
ON/OFF contrast and ANSI contrast are the two extreme ends of the contrast range that applies to video content. The ON/OFF Contrast only provides the black level of a completely black picture (full field black). Similarly, the ANSI Contrast only gives you the black level at what is typically the extreme upper limit of video content brightness. Where 99.5% of video content falls in-between these.
Consequently, in order to properly evaluate and understand what is the comparative contrast and associated black levels performances regarding different video display devices, including projectors, we need to take measurements with respect to the whole range of ADL (Average Display Luminance), being defined as the average on-screen brightness after gamma correction.
ON/OFF contrast corresponds to an ADL of 0%; and ANSI contrast corresponds to 50% ADL.
The average ADL of movies is 8% – 9.6%.
Here is an illustrative example; where this particular image measures 5.9% ADL:
Circa 73% of video content resides within the range 0-10% ADL; 82% within the range 0%-15% ADL; 91% within the range 0%-20% ADL; and 99.5% resides within the range 0%-50% ADL (ANSI), with only 0.5% residing within the range 50%-100% ADL.
|RANGE||%AGE OF VIDEO CONTENT|
Hence why it is all-important to measure and analyze the full range of contrast measurements. Not just the ON/OFF and ANSI contrast, but everything in-between as well.
By way of an example, here are the full range contrast measurements of three projectors:
Thank you to Florian Auté & Anna Landes of Projection Dream for their published study: “Brightness of movies (ADL) and contrast measurements”.