Posted on March 26, 2018 By Art Feierman
BenQ HT2550 Low Cost 4K UHD Projector Review – Special Features: 4K UHD, 4K HDR, Silence Mode, REC 709 vs P3/BT.2020, Color Wheel and Rainbow Effect
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).
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.
Most 4K UHD projectors, and for that matter projectors that can accept 4K content, support HDR – High Dynamic Range – (not all on the business projector side, and even one home theater projector I can think of lacks HDR support).
HDR is a challenge for most LCD TVs and home projectors because it calls for a lot of brightness, so there’s more range between black and white – less compression of the original scene.
With the possible exception of Sony’s $60,000, 5,000 lumen 4K projector, the VW5000ES, everything else out there definitely needs more lumens. That Sony produces over 4,000 lumens in best quality modes, whereas most of these produce 1,500 lumens or less in their best modes.
As a result, projectors (and many LCD TVs) can’t really do the full HDR, so they compromise. This first year, the compromises have been very different from one projector to another. Usually, the tendency of not having enough brightness is that mid-range bright objects are too dark, or as I sometimes say, “too dim.” One can correct for that, but doing so effectively also reduces the advantage of HDR.
Consider – the HT2550 is pretty typical, leaning on the slightly dark mid range (and below). Epsons are even darker. Optomas I’ve worked with are brighter, but look less different compared to non-HDR, than those which have the darker tendencies. The HT2550, I believe, came up with a good compromise – just a bit dark, so maintaining some good pop, from the whole HDR aspect.
Silence mode had me stumped. Who names a mode Silence, when they already have ECO modes, etc., on the lamp? So, I cracked open the manual. It is the quietest mode, but it is not materially different from ECO lamp. I really didn’t pay attention because it’s reasonably quiet in either of those modes.
But, worth noting, is that Silence mode turns of pixel shifting! Best I can tell, it seems to be the only way to turn off pixel shifting. When you do that, you have, essentially, a classic 1080p projector. Other than playing with it for a few minutes, I didn’t use it. I use other modes and let the projector pixel shift 1080p and other “lower” resolutions.
If, however you desire 1:1 pixel mapping – for the sharpness natural image from the data, go for it. The whole point of pixel shifting, si that by using more pixels, it can more closely behave like a projector using smaller (higher native resolution) pixels. In a sense, by using Silence mode, you are making the HT2550 perform sharpness and detail wise, like BenQs very nice sub-$800 1080p projectors.
To take full advantage of the 4K suite of standards, it’s not just the 8.3 million pixel requirement, but the ability to do both HDR, and also a larger color space. There’s BT.2020, which is the maximum, but I don’t even think the cinema projectors in you local theater have enough range to fully do BT.2020 (which gives richer, more intense, and more colors to work with).
That’s okay, there’s a “subset” called P3. I here engineering types refer to it as “P3 in a BT.2020 wrapper.” These days P3 expanded color is obtainable, although lamp based projectors generally can’t get close, (they barely get to REC709, the standard we’ve been using for the past couple of decades – this BenQ claims 96% of REC709). Far better equipped to do P3 are laser projectors, or LED projectors (like BenQ’s HT9050 which supports P3).
Some lamp projectors talk the BT.2020 / P3 game, but best they can do is take all the BT.2020 info and convert it down to REC 709, surrendering all the advantages that BT.2020 promises. BenQ mentions BT.2020, but, ultimately, they also say they have great color, which achieves 96% of REC 709 (which is probably no more than 70% to 75% of P3, if that).
BenQ’s HT2550 knows what to do with BT.2020, but it produces REC709, even when the content on disc, or download, or other 4K source, provides the BT.2020 color space.
In that regard, it’s about the same as just about all of the lamp based projectors around this price range. There’s an exception – Epson’s 5040UB ($2,699 list). It adds a cinema filter, which helps, in its best mode. Epson, therefore, does a lot better than the rest (or at least those we’ve worked with), but – and I mean a big but: that cinema filter eats up about half of that Epson’s lumens, reducing it to about 1,000 lumens. That’s still, though, about 20% brighter less than this BenQ in its best mode. That’s the trade-off: The Epson can get closer to P3, but it has less lumens doing so, which means more compromise when doing HDR, but then, remember the Epson is an extra $1000 and change.
Bottom Line: The BenQ HT2550 gets some dynamic boost using HDR, but color space, as with most of these projectors, ends up basically the same as the 1080p projectors we’ve been using for the past decade.
Folks there are always compromises!
Ah, thank you BenQ. I’ve said this over the years, and it’s still true. In most cases, compared to other home DLP projectors, at a given price point, BenQ seems to almost always provide a faster color wheel, and that’s a real bonus for those of us who are rainbow sensitive (that’s called RBE). I’ve never seen info as to what percent of the population is sensitive to them, but my best guess is around 5% maybe 10%, max. So, it’s likely you won’t be, but if you have a bunch of people watching with you, someone is likely to be sensitive.
I am one of those, so with single chip DLP projectors, I will see occasionally flashes of color from time to time, with the frequency, and the amount of distraction dependent on the speed of the wheel (and also the type of content – a fast moving white object on a black background is perfect for seeing “rainbows”).
BenQ boasts a 6X color wheel. Most of the 4K UHD competition is using 2X or 3X. 2X projectors drive me crazy, and for home theater, I personally wouldn’t buy any projector with 3X either, too much distraction! But “6X” works for me. 6X really should be 5X in the US (the wheel, I figure 6X where the AC electricity is 50hz such as Europe, while it would be 5X because of 60hz AC in the US).
No matter, with this projector, rainbows are rare. Oh, if I shake my head, I can force some. But not doing so, I might even get through a whole movie without seeing one, or perhaps a couple flashes on a scene or two. That, I can live with (and have in the past). I would no longer consider personally buying any home projector with a 2X or 3X wheel. Too much distraction!
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