In general we treat these two together, because there are often trade-offs between them. I consider Black levels to be the more important of the two (by far), but you do want your projector to at least be good at preserving and showing dark shadow detail.
It’s black levels however, that I oft refer to as “the Holy Grail” of home theater projectors. It is often the primary difference between great projectors and mediocre ones.
What you need to know is this: Comparing projectors with great vs mediocre black level performance, will reveal huge differences on very dark scenes, but only slight differences on bright scenes. Unlike the old style CRT projectors, today’s modern (fixed panel) projectors all output some light when black – no light – is called for.
The brighter the “blacks”, the worse dark scenes will look. And the difference can be rather dramatic to say the least. Here’s one picture showing a typical $1600 projector’s black level performance on a dark scene, and a $2600 projector doing the same, but that one has the best blacks of any projector near its price.
The loss of a small amount of the darkest shadow detail is rarely a noticeable problem. Once in a while, you might hit a scene where there might be a telling difference between great dark shadow detail and only decent, but mostly if your dark shadow detail is only good, or very good, you wouldn’t be likely to notice it. It’s easy to spot, though on scenes like the one above, comparing the woods and shrubs on the right side of the Bond Train scene.
In general, the blacker the blacks the less you’ll notice some small loss of dark detail. Personally, when controls are a little coarse (not uncommon) you’ll have a choice by adjusting brightness plus or minus one. With the lower setting you get a bit better blacks but some minor crushing. With the higher setting (by one) the blacks will be a touch brighter, but the slight missing dark shadow returns.
FYI: Adjusting the black levels to get the best blacks is done with the Brightness Control. But it will typically affect dark shadow detail as well. The trick is to balance best possible blacks against a possible slight loss of dark shadow detail.
On this dark scene, you've got not great/washed out/flat black levels (left - Panasonic PT-AR100U) vs. "excellent" black levels (right - Epson Home Cinema 5010).
On this dark scene, you've got not great/washed out/flat black levels (left - Panasonic PT-AE8000) vs. "excellent" black levels (right - Sony VPL-HW50ES).
Here are the same two projectors on a more typical and far brighter scene, and they may be close to indistinguishable from each other.
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