The BenQ HT2550 is another 4K UHD projector, and this is the year for them (okay, started last year). So, here’s another explanation of this projector’s 4K UHD as it compares with other 4K capable projectors:
4K UHD standard says a projector needs to put 8.3 million pixels on the screen to be 4K UHD. Sadly, the CTA standards folks (that’s the organization that puts on the CES trade show), did not specify how large those pixels can be, so they allow “pixel shifting.” That is, starting with panels or chips that have less pixels than 8.3 million. Some 4K UHDs have panels/chips with 4.15 million pixels – 2716 x 1528 x2 native resolution – and fire them twice, shifting position diagonally so that the second firing overlaps the first. Typical of those projectors are BenQ’s higher end models, and some models from Optoma, Acer, Vivitek, and so on.
Then, there’s the newer, lower cost 4K UHD projectors like this HT2550 (the first of these to ship), which have 1080p panels, just like most of the home theater projectors sold in the last 8-10 years. The difference between these and “most of those” is that these are also pixel shifters, but they fire each pixel 4 times, each overlapping the others. So, their native resolution looks like 1920 x 1080 x4. That, too, works out to 8.3 million pixels (just over 2 million times 4).
The top image is the Optoma UHD60, which uses the higher resolution 2716x1528x4 pixel shifting DLP chip.
Overlapping pixels can increase detail, but do understand that each pixel in diameter on this BenQ is 4 times the size of one pixel on a native 4K projector, like Sony offers, starting at $4,999. Even the higher res 4K UHDs have pixels twice the size. So, when it comes to max detail, think this way: Pixel size is still the most important thing. When considering the different pixel sizes, native 4K (3840 x 2160) think of a baseball, for the 2716 x 1528 x2, think of a softball, and for these 1920 x 1080 x4 projectors, think of a six inch diameter ball (I can’t think of any sport that uses one that size – still, the analogy should help).
And again, below this “resolution” are the 1080p pixel shifters that only hit the screen twice (from Epson, JVC, etc.).
Bottom line: To a large degree, the differences between all four are slight, with each step up providing some improvement. Remember, how well each projector implements, matters. Sony, for example has 5 native 4K projectors, but the more expensive ones have better optics, etc. So, it comes down to how well each projector is implemented. Epson, for example, is the lowest res (along with JVC), but has some impressive image processing. BenQ’s high end has better optics than you can expect from all the $1,500 to $2,500 4K UHDs, etc. We’ll discuss the actual sharpness performance on the Picture Quality pages.