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Optoma UHD51A 4K Home Theater Projector Review: Performance

Posted on July 29, 2018 by Art Feierman

Brightness Of Picture Modes

Picture Modes Pre-CalibrationLumens
HDR Sim1063

Compared to the 2500 lumen claim the UHD51A clocked in down about 20% in the very brightest mode (named Bright mode), from claim, with a 1988 lumen maximum.  Unfortunately, Bright mode is pretty unusable, it is so green.  Usually I say that a mode like this is a "break glass in case of emergency" mode, to be used only when overwhelmed with ambient light. This Bright mode, however is probably best never used.  If you can't watch the content in a different mode, best to find a smaller LCD TV to watch.

With that said, let's look at the other modes.  All but Reference fall between 1063 lumens and 1310 lumens, which is plenty for all normal viewing on typical screens to 130" diagonal, no problem.  4K when using HDR, is its own separate thing, which, like 3D wants more lumens.  Fortunately HDR mode is the 2nd brightest and it lost only a handful of lumens with calibration, still measuring in at 1254 lumens a drop of almost exactly 5%, which is to say:  Not noticeable!

Reference mode which Eric calibrated as our best mode for non-4K/HDR, is, again, the least bright, but its 780 lumens "right out of the box" in Reference, increased to 834 lumens post calibration.  That's mid-zoom, so the projector is approaching 900 lumens with the lens set to wide angle.  That's about double the lumens needed with a 100" diagonal screen for typical movie viewing in a dark room!  Still it's nice to have lumens to spare.

Jumping back to HDR - can't have enough lumens for that (5000 lumens would be about right for a 100" screen in a perfect world), but as mentioned elsewhere the HDR implementation on this projector in terms of being bright enough so as to not often seem dim, is a good one.

Effect of Zoom Lens on Brightness

The UHD51A's manual zoom lens has a 1.3:1 ratio, which is relatively limited. Many of the 4K UHDs have 1.2:1 o 1.3:1.  That doesn't provide much distance flexibility when it comes to placement - only 2-3 feet depending on the projector - from closest to furthest away - when considering a 100" diagonal screen.  Those projectors with a lot of range might have 6 or even 10 feet of placement.

That said,its only a problem if you are mounting, and can't place the projector where your room requires it.  In that case, you'll have to punt and buy a projector with better suited placement flexibility. Still most under $2000 projectors have about this much, only a few (Sony with 2.1:1) and some Epsons really have a lot more.

Because the zoom range is so slight, there's only a brightness drop of about 16% from closest placement to furthest.  That's pretty slight, just noticeable.  By comparison most eco modes drop brightness 25-35%.   A projector with 2:1 zoom is likely to lose something around 30% maybe more from one end of the zoom range to the other.

So, not enough brightness loss to be concerned with - place this projector where it is most suitable based on other issues.

Lens controls
Effect of Zoom Lens on Brightness - All modes with have the same ratiosLumens
Wide Angle (closest to projector)1988
Telephoto - furthest from PJ1726

Effect of Eco Mode on Brightness

Optoma offers two modes basically full power, and Eco.   In addition, there's the Dynamic Black I have written about, for doing lamp dimming to enhance black levels on less bright scenes.

Unfortunately, although not surprising, Optoma's configuration doesn't let you run Dynamic Black in Eco mode.  So, for the most part, when using Dynamic Black, you'll be running at full power, and with full fan noise etc.  Still on darker scenes the Optoma may quiet down a bit. Good thing this UHD51A starts out a little bit quieter than most of the competition.

Here are the numbers, measured using Bright mode (mid-zoom):

Full power: 1892 lumens
Eco mode: 1265 lumens

In other words, selecting Eco mode (but sacrificing best black levels), will reduce brightness by about 1/3, which is fairly typical.   Looking at it the other way, Full Power is almost exactly 50% brighter than Eco.

With Dynamic Black running, most brighter, and mid-range  scenes will prevent any lamp dimming from occurring, so for most watching with Dynamic Black on, all the lumens are available.

Post Calibration Color accuracy (best mode)

Eric will discuss in greater detail for the more technical of you.  So I'll just mention here, that the color in best mode - calibrated Reference, and also in our 4K UHD modes look really very good - almost excellent, and very good respectively.  (Yhese are my subjective opinions of course.)

When a projector has slight inaccuracies it can look absolutely great - on the money - on some content, then not quite as good on others. A projector with flawless post calibration picture should look equally good on all content, not just some. To better explain, I'll regress to my high end audio days. They say there are great rock speakers, great jazz speakers, great speakers for vocals, great for orchestras. That is, some speakers are particularly good at some things. But the truly accurate, faithful speaker will sound great on all types of music, because voices won't sound too distant or too close, Bass won't be too much, or too little for different types of music.  I could go on, but you get it.

Bottom line, only the most hard core should take any issue with the overall color which at the least, is very, very, good post calibration.


Sharpness 4K Content

OK, fun and games time with sharpness, perceived sharpness, detail, etc.  I've discussed a bit in the Special Features pages, but here we'll post a variety of images and then close ups.

I will focus on 4K content, since any 4K capable projector should do at least a really good sharpness job on 1080p and lower resolutions.  The only exception is the last image, Which I'll discuss at the end of this section.  The close-up versions are good representatives of actual sharpness, if you click, and then expand again.

After the first couple of image/close-up images (4K disc), the third pair - is from Blacklist streaming on Netflix in 4K (no HDR).  Next I have provided a large collection of comparison images of the lab/credits in Ghostbusters 2016 (4K UHD Blu-ray).  After the UHD51A, in order, those close-ups are:  BenQ TK800, and the Viewsonic PX727-4K (both use the same DLP chip as the UHD51A), then comes the laser projector, the Acer VL7860 which uses the higher resolution 4K UHD DLP chip.  That's followed by the Vivitek HK2288 (same chip as the Acer).  Next we leave DLP and check out Epson's 5040UB, which is 4K capable but uses a 1920x1080x2 chip (and is a touch less sharp.  Sony's VW385ES comes next - true 4K LCoS chip, $7999, this one shares the same lens as Sony's entry level. Finally Sony's $15K VW885ES. (Sony's get sharper as you spend a lot more, thanks to better lenses).

The last few images are renderings of the Bigalow space station in Journey To Space. A shorter collection here, just the Optoma 51A and Viewsonic, the Optoma UHD65 with its bigger chip, and lastly the Epson 5040UB.  Then Saturn, of course, and our one football close-up.

The one 1080i resolution image close-up you see as the last image, is a close up of part of a 8 football game Game Mix on DirecTV.  While the small test in individual games is a bit rough, you can pretty much read everything that was on a single televised game, even with that one game occupies less than 10% of the full screen. (That's pretty darn good!).

Image Noise

Pretty typical of today's projectors.  Mosquito noise - basically a background noise spottable in large bright consistent areas, is typical of the 4K UHD projectors.  Also typical was the handling of the scene from RED that I use as a slow panning test.  That is to say, everything was vibrating during the pan, but I've seen a good bit worse, even on $25K Sony 4K projectors.

CFI generates noise around moving objects but that's expected, and its minimal on the Low setting.

Bottom line: Nothing jumped out at me as a problem.  I stopped using test discs a few years back as rarely does a serious projector show up with a real problem.


Audible Noise

I was pleasantly surprised to find that the UHD51A is definitely not as noisy as its competitors from Viewsonic and BenQ.  In my review of the TK800 I narrowed it down to that it seems like this 4K UHD DLP chip and assembly is "humming" from, what I suppose is the pixel shifting. The DLPs with the step up DLP chip, only have to shift once, these shift three times.

For whatever reason, perhaps the slightly larger case, or the internal sound baffling, this is much improved, compared to the others.  They all seem to have about the same amount of fan noise, but the hum rises to the top with the others. None of these DLP projectors are considered really quiet at full power.  By comparison the $2K Sony is probably quieter at full power than this Optoma is in Eco mode, and that's a real difference.  Still, most home projectors these days are trying to put out more lumens, and be smaller, so its harder to keep them quiet.  If you tend to be noise adverse, and would run Eco, remember to use Dynamic Black you can't run Eco so it will mostly run at full noise levels.

For most of us, its acceptable at full power, and fairly typical.

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