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Establishing of Baseline of Real Comparison

As you probably already know, the contrast specifications on projectors are not reliable guides to the real contrast you experience when viewing the image on the screen. A primary reason for this is that when the projector has an automatic iris, "full on/full off" contrast measurements yields different results when the iris is on and when it is off. It is not always clear from the specs whether a projector has an auto iris, or if it does, whether the contrast rating was done with that feature activated or not. If the auto iris is off during the contrast reading, it will inevitably yield a lower number, normally referred to as native contrast.

There is an alternative to the full on/full off method of contrast measurement. We can use a black and white checkerboard pattern and measure the ratio of the whites to the blacks. This is the ANSI Contrast procedure, and it tends to yield lower contrast readings than full on/off. The good news is that it is the most effective way to determine a projector's potential dynamic range within a given scene. Unfortunately, the vendors generally decline to publish ANSI contrast specs because it will put them at a serious competitive disadvantage with consumers who don't understand the differences in how the readings are being taken. Furthermore, as a practical matter, the ANSI contrast spec is not a panacea either. It does not take into account the positive effects of an auto iris which can in fact be beneficial in terms of overall perception of contrast. The bottom line is that there is no way to generate a single contrast specification that will have equivalent meaning across all types of projectors.

Nevertheless, we are going to begin publishing ANSI and native contrast specs on all of the projectors we review. In order to take accurate contrast readings, one needs a black, non-reflective space so that black levels are not polluted with reflected light from the white squares in the ANSI checkerboard pattern. This is what we've been working on this past week, and it is taking us a while to get it squared away. But since we have on hand the BenQ 20000, rated at 20,000:1 contrast and the JVC DLA-RS2 rated at 30,000:1, we have the perfect opportunity to inaugurate our ANSI and native contrast measurement procedures with two of the highest contrast models currently on the market.

By adding contrast measurements to our reviews, we will be able to establish a baseline of real comparison between models and help to eliminate the confusion that exists with some of the current full on/off specs as published by the manufacturers. We will get the BenQ 20000 review completed as soon as we get our ANSI contrast testing space completed.

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