The $1,699 BenQ TK850 (offered promotionally at $1,499 as of this posting) and $1,799 Optoma UHD52ALV 4K projectors are about as directly competitive as two projectors can be. Both support both HDR 10 and HLG versions of HDR and both deliver 4K resolution courtesy of a 0.47-inch TI DLP XPR chip, which puts 3840x2160 pixels on screen using TI's fast-switching pixel-shifting. But the most critical feature they have in common is the white panels in their color wheels, which boost brightness at a small cost in color accuracy.

The boost from these white panels make both projectors strong candidates for rooms with ambient light, where brightness matters more than contrast or dead-on color accuracy. In short, they're both potential choices for your family room as a replacement for your TV. And if you want larger-than-typical screen size in a traditional home theater, they can serve in that capacity also. Both deliver good enough color accuracy so most people wouldn't notice any color errors without a side-by-side comparison with a reference image.

The long list of features both projectors offer includes 1.3x zoom lenses, support for full HD 3D with DLP-Link glasses, frame interpolation for smoothing motion, two HDMI 2.0b ports with HDCP 2.2, built-in USB media players for up to 4K video playback, onboard stereo audio with two 5-watt speakers in each case, and both S/PDIF optical audio and 3.5mm outputs to connect to external sound systems. But they also have lots of differences.

Key Spec and Features Differences

Brightness. One obvious differences is that the UHD52ALV is brighter, but the advantage on this score is more nuanced than you might think.

The Optoma projector bests the BenQ TK850 in rated brightness, at 3,500 ANSI lumens compared with 3,000, as well as in measured brightness for the brightest mode available, at 2,965 lumens compared with 2,544. More important, for the brightest SDR modes for each that offer good enough color accuracy so most people would find them acceptable straight out of the box, it delivers higher brightness. For the UHD52ALV, we measured a little over 1800 lumens for Cinema and User modes. For the TK850 we measured 1,550 lumens for Cinema and Sports modes.

Keep in mind that the perception of brightness is logarithmic, so it's the percentage difference for each comparison that matters rather the raw number of lumens. In addition, a difference of 10% or less is too little to notice unless you're looking at side by side images.

In this case, the UHD52ALV is about 16% brighter than the TK850 for both the brightest mode and brightest most-likely-be-used modes—more than 10% but not a lot more. Doing the math shows that if you need, for example, a 50 ft-Lambert (ft-L) image brightness and want a 110-inch screen, you can get it with 1,800 lumens and 1.0-gain screen or 1,550 lumens and 1.2 gain screen. Alternatively, you can stay with 1.0 gain for 1,550 lumens, drop the screen size to 100 inches, and get 52 ft-L. In short, for any given image size and screen gain, the Optoma UHD52ALV will you the brighter picture in comparable modes, but not enough brighter to matter much in a practical sense.

The same comments apply to HDR brightness. On my 90-inch, 1.0-gain white screen, I measured the HDR image brightness for the UHD52ALV at 227 nits, compared with 192 nits for the TK850.

Silence mode. The TK850 offers a Silence mode, which eliminates upscaling of 1080p input to 4K in favor of quieter operation. Using this feature largely defeats the benefits of buying a 4K projector for an improved image, but if you plan to use Silence mode, note that it's also the projector's least bright mode. The UHD52ALV has no equivalent feature.

Resolution. The native resolution for both projectors is the same 3840x2160 and both support that resolution at 60Hz. But the maximum input resolution for the UHD52ALV goes one step further, to 4096x2160 at 30 Hz.

Color wheel. The UHD52ALV's RGBWRGBW's color wheel cycles through its colors twice for every rotation, compared with the TK850's RGBW wheel's once. All other things being equal (and keep in mind that there are lots of other factors involved), this doubles the speed of each repeating color sequence in the UHD52ALV to minimize the visibility of rainbow artifacts. This is likely at least partly responsible for my having seen notably fewer rainbow artifacts with the UHD52ALV than the TK850.

Smarts. The UHD52ALV offers several smart features under the umbrella of Optoma's Smart+ technology. It includes voice control using Alexa and Google Assistant; IFTTT (If This Then That) compatibility, which lets you set up IFTTT applets; and Optoma's InfoWall. The applets let the projector do tricks like automatically mute the volume when someone rings your smart doorbell or calls your smartphone. InfoWall works with a free app that lets you define a customized set of tiles, or information templates, that can show your choice of weather reports, news, your calendar, YouTube videos, or photos you've stored online. The TK850 doesn't offer any smart features.

Contrast ratio. The specs for contrast ratio for these two projectors differ by more than an order of magnitude: 500,000:1 for the Optoma UHD52ALV compared with only 30,000:1 for the BenQ TK850. But you shouldn't take these numbers too seriously. Different manufacturers often measure contrast ratio differently, and a single manufacturer will often measure it differently for different projectors.

Beyond that, even if the specs for both projectors are measured the same way, the difference won't mean much for lights-on viewing. Ambient light washes out black, leveling out the black-level differences between projectors and making brightness the more important factor in contrast ratio. Even an ambient light-rejecting screen can do only so much for contrast in lights-on viewing, since its light rejection is limited to light coming from a specific direction.

Dynamic iris. The TK850's 30,000:1 contrast ratio is based on using its dynamic iris, which adjusts automatically based on the current image to help make dark scenes darker and bright scenes as bright as they can be. Settings of Low, Middle, High, and Off let you adjust it to taste. The UHD52ALV lacks a dynamic iris, but offers a Dynamic Black mode, which is meant to have the same effect on brightness by adjusting the power level. Dynamic black has only on and off settings. Much like the TK850's contrast ratio rating, the UHD52ALV's 500,000:1 spec is based on contrast with Dynamic Black turned on. Note that you can use the TK850's dynamic iris in either full power or Economic mode. The UHD52ALV's Dynamic Black mode is available only with full power.

Lens/Image detail and sharpness. BenQ touts the TK850's 10-element, 8-group lens array on its website as a premium 4K, precision lens that uses "the highest-grade glass for superior...image quality." Optoma makes no particular claims for its lens but touts its UltraDetail technology, which it says ensures the image is "accurately reproduced...to give a stunning crystal clear, pin-sharp picture." In side-by-side viewing, I didn't see any difference in image detail or sharpness except in cases where one projector or the other delivered enough higher contrast to make detail stand out better.

Color Accuracy. Neither of these projectors can deliver a high degree of color accuracy while still maintaining high enough brightness for lights-on viewing or for a larger-than-typical screen in the dark. However both deliver color accuracy with default settings that most people will find more than acceptable. Few will even notice any color errors without a reference image to compare with.

The biggest difference between the two projectors on this score is that if you want to get the best color accuracy possible from them, the TK850 is a lot easier to calibrate. The UHD52ALV adds unnecessary obstacles to the process, including the need—as detailed in the UHD52ALV review—to manually re-enter settings for each video source you use.

Note too, that we couldn't find any settings for the UHD52ALV that let it reach the generally desired target measurement for color errors. And as detailed in the BenQ HT3550 v BenQ TK850 comparison, we were able to calibrate the TK850 to that level only with settings that brought brightness down to 429 lumens—just enough for a 90-inch, 1.0-gain screen in a dark room.

Input Lag. The input lag is a bit slow for even casual gaming on either projector. For 1080p, the measured lag was 82 ms for the TK850 and an only marginally better 75 ms for the UHD52ALV. For 4K, the measured lag was 86.5 ms for the TK850. The Optoma projector didn't recognize our 4K/1080p Bodnar meter at 4K, but Optoma says the lag should be the same at 4K as at 1080p—about 75 ms.

Lens offset and lens shift. Both projectors have lens offsets and lens shifts designed to work best with the projector in a ceiling mount or on a table just below the bottom of the screen. The UHD52ALV has a slight ease-of-setup advantage, however, letting you shift the image vertically by a total of 15% of its image height, compared with 10% for the TK850.

Lamp Life and Cost. Lamp life is similar for the two projectors, at 4,000 hours in full power mode, 10,000 hours in Eco mode, and 15,000 in the UHD52ALV's Dynamic Black mode or the TK850's SmartEco mode. The TK850 has the edge on lamp-replacement cost, however, at $149 compared with $249.

Wireless display. Both support wireless display from mobile devices. The UHD52ALV comes with one Wi-Fi dongle. You can also buy another and use both at once, connecting wirelessly to a mobile device with one, and to a network with the other for Alexa or Google Assistant. BenQ offers an optional HDMI dongle for wireless connection to mobile devices.

Warranty. The TK850 earns points for its 3 year warranty and 1 year on the lamp. The UHD52ALV includes only a 1 year warranty with 90 days for the lamp.

Image Comparisons

1080p/SDR Viewing. For the side-by-side comparisons, I first calibrated both projectors. For 1080p SDR content, getting the best color accuracy from the BenQ TK850 lowered brightness to 429 lumens. Actually using it that way would make it pointless to have chosen a projector that includes a white panel to boost brightness, and would also have put the TK850 at a tremendous disadvantage compared with the UHD52ALV's much brighter picture. Because of that, I readjusted the Brilliant Color setting to minimize the difference in brightness for SDR content.

Note that the default setting for Brilliant Color on the TK850 is 10. To get the best color accuracy—which was better than I was able to get at all with the UHD52ALV—I had to turn Brilliant Color off. For my side-by-side tests in a dark room, I set the UHD52ALV power level to Eco and raised the Brilliant Color setting for the TK850 to 4, which gave both images a subjectively similar brightness level.

The adjustment to the Brilliant Color setting also gave the TK850's picture the slightest of green biases, but it was little enough so most people wouldn't notice it without a reference image to compare with, and not enough to make colors in any of the movies I tested with look unrealistic.

Also keep in mind that lowering the degree of color shift for the TK850 or removing it entirely is a simple matter of lowering the Brilliant Color setting, so you can adjust it to whatever compromise between image brightness and color accuracy you like. And even with Brilliant Color set to 10, the color errors were no greater than the best color accuracy I was able to get with the UHD52ALV, which was slightly red shifted.

For the side-by-side comparisons, I viewed a variety Blu-ray discs as well as movies and filmed TV shows on Netflix. I was able to see the images simultaneously in all cases—for SDR, HDR, and 3D--using a splitter. I also did the comparisons in a dark room, a dim room with only one floor lamp on, and in ambient light more typical of a family room at night—the last two lighting conditions being what both of these projectors are really meant for.

In a dark room, I saw no difference in black level or shadow detail, and no consistent difference in contrast. In my go-to dark scene in Batman v. Superman, where the young Bruce Wayne falls into the bat cave, both images showed virtually identical black levels and shadow detail in the barely lit rocks. The only noteworthy difference between the two was slightly better contrast for the UHD52ALV thanks to brighter reflections in the bats eyes.

In scenes dominated by midtones, both delivered closely matched contrast in all scenes, with each one having slightly better contrast than the other depending on the lighting of each individual shot. For the content I tested with—including The Martian, The Secret Lives of Pets, and the first episode of Lucifer on Netflix—the Optoma UHD52ALV had better contrast on more scenes, but not every one and not by a lot. Neither had the level of contrast that gives a three dimensional look to the image.

Either projector viewed by itself did well enough on color accuracy, contrast, and black level so that most people would judge the picture as more than acceptable with no obvious flaws. But for dark room viewing, neither is a match for projectors that are designed primarily for traditional home theater.

Note that in shifting my gaze back and forth between the images—which tends to cause rainbow artifacts from the eye movement—I saw artifacts with both projectors in scenes with high contrast, but they lasted longer, and were more frequent with the BenQ image. If you aren't particularly sensitive to or bothered by rainbow artifacts, this won't matter, but if you are, it may.

In dim lighting, the difference in contrast between the two disappeared. In one bar scene early in the Lucifer pilot, for example, with Lucifer partially backlit by a spotlight, the contrast difference went from slightly favoring the UHD52ALV to no difference at all when I turned on the floor lamp.

For testing in brighter light, including overhead floodlights, I also boosted brightness for both projectors, so they could stand up to the light better. For the TK850, this meant setting Brilliant Color to 10. The green shift was still not enough to be obvious, but in side-by-side viewing, flesh tones looked more natural with the UHD52ALV image.

For the UHD52ALV, boosting brightness meant switching to full power mode—or the equally bright Dynamic Black—which gave it a tremendous advantage. Even in Eco mode, the UHD52ALV's picture was a little brighter than the TK850's, particularly in darker scenes like nighttime shots of city streets, when Lucifer's friend is shot. Switching the Optoma projector to Bright or Dynamic Black only increased the brightness difference between the two.

Ultimately, movies were eminently watchable with lights on with both projectors, but the UHD52ALV was noticeably brighter and delivered noticeably better contrast in both dark scenes and more brightly lit scenes, like the outdoor wedding that Lucifer interrupts.

Note that repeating these tests using a 110-inch Screen Innovations Slate 1.2 ALR screen (1.2 gain) improved both projectors' perceived contrast in ambient light, making the UHD52ALV's higher brightness less of an advantage. More precisely, it improved the contrast for both projectors, but improved the TK850's image more, so there was notably less difference between the two. Depending on the screen size, using an ALR screen can also eliminate the need to crank up the TK850's Brilliant Color level, and the green shift with it.

UHD/HDR Viewing. The conventional wisdom is that most projectors aren't bright enough for HDR content to stand up to ambient light at the image size you likely want from a projector. With that in mind, I chose settings for UHD/HDR viewing that coax as much brightness as possible from each one and as dark a black as possible in dark scenes.

For the UHD52ALV, that meant turning Dynamic Black on, which is basically full power mode with automatic power adjustments to emulate an auto iris. For the TK850, I used full power mode, left Brilliant Color at its default 10, and turned the Dynamic Iris on, using the Low setting. I also adjusted the HDR brightness for each as needed for each movie I tested with, as well as for each light level.

In a dark room, the TK850 delivered better contrast, black level, and sense of three-dimensionality than the UHD52ALV in every movie I tested with, including some that are filled with dark scenes, including Batman v Superman; others crafted with vibrant color, most notably La La Land; still others with more subdued color, including Arrival, and even animated features, including The Secret lives of Pets.

The TK850's advantage was obvious from the first shot in the first scene I looked at, which was the funeral scene at the opening of Batman v Superman, with the casket being carried across a lawn filled with orange-brown dead leaves. The TK850's image had the far better contrast of the two, which also gave it the better sense of crisp focus and three dimensionality. Each leaf on the ground stood out from the grass, and the black coffin was both darker than in the UHD52ALV's image and did a better job showing off its piano-black sheen.

Similarly, when the young Bruce Wayne falls into what will become the bat cave in Batman v Superman, the backlit silhouette of the boy falling was far darker in the TK850's image, and the backlight was dramatically brighter. And in my go-to dark scene for testing, showing myriad bats hanging upside down, there was no comparison between the two. The TK850 delivered a dramatic image, with far darker black than the UHD52ALV's version and a significantly better sense of three dimensionality.

Color differences between the two projectors weren't significant. The colors were more closely matched more often with HDR content than with SDR content. And to the extent that they were different, the differences varied from shot to shot. More important, as with SDR content, the colors with either projector were more than acceptable for normal viewing, and the differences were obvious only because the two images were side by side.

Colors were also vibrant and well saturated when they should be for both projectors, as demonstrated in La La Land, which is filled with almost nothing but vibrant, saturated colors. Most notably, both projectors did a good job handling yellow, a color that DLP projectors often have problems with. However, the UHD52ALV's yellow for the dresses in the dance scene on the highway was a more accurate, brighter yellow than the TK850's slightly darker version.

With dim light, the higher brightness for the UHD52ALV became almost as important for contrast as the TK850's inherently darker black. With the black levels somewhat washed out by ambient light, the TK850 had almost no advantage in contrast, black level, or three-dimensionality in bright scenes. There was no longer any sense of sharper details in the TK850's image for the outdoor funeral scene, for example, and the black casket looked nearly identical for both projectors.

The black silhouette of the falling Bruce Wayne was still a little darker for the TK850 and the bright light a tad brighter, but I had to pause the movie and look carefully to be sure. And the shot with the hanging bats—complete with glowing eyes and shadow detail—was essentially a match between the two projectors until the titles disappeared from the screen, making the image dark enough for TK850's auto iris to kick in. At that point, the black level in the TK850's image became a tad darker and the contrast a tad better than in the UHD52ALV's image.

In brighter lighting, the contrast advantage shifted to the UHD52ALV, with contrast for the side-by-side images matching in most scenes, and the UHD52ALV offing the better contrast in scenes where there was a difference. Even in the dark scene in the bat cave, there was no significant difference between the two projectors.

Also note that when I ran the lights-on tests using the ALR screen, the contrast improved for both projectors. However, the only differences it made to their images relative to each other were to further increase the UHD52ALV's contrast advantage in those scenes where it already delivered the better contrast between the two.

3D Viewing. Both the TK850 and UHD52ALV support Full HD 3D. Both deliver highly watchable images with saturated color, and I didn't see any crosstalk with either in my tests. However, I saw only the typical level of 3D-related motion artifacts for current generation projectors with the TK850, and saw them a little more frequently with the UHD52ALV. On the other hand, the UHD52ALV's higher brightness extends to 3D as well, which is arguably more important for a projector intended for lights-on use. Neither projectors' frame interpolation (FI) feature is available for 3D content.

Conclusion

The BenQ TK850 and the Optoma UHD52ALV each deliver better image quality than the other—and more specifically better contrast, black level, shadow detail, and image sharpness than the other—in some conditions. That makes choosing between them a little complicated. You might want to start by deciding what kind of screen you plan to use—a standard screen or an ALR screen—and then consider both the ambient light levels you expect to use the projector in and whether you care more about image quality with 1080p SDR or 4K HDR.

With a standard screen, both projectors were closely matched for 1080p SDR image quality with both dark and dim ambient light in my tests, although the UHD52ALV had a slight edge in contrast in the darkest of dark scenes when viewed with little to no ambient light. With moderately bright ambient light, however, the UHD52ALV's obvious advantage in brightness also translated into notably better contrast. All of which makes the UHD52ALV equal to or better than the TK850 for 1080p SDR content regardless of ambient light level.

What makes the choice harder is that the same is not true for 4K HDR content. In my tests, the TK850 delivered notably better contrast, black level, and three dimensionality in a dark room, and did slightly better on all three scores with dim lighting. It was only with brighter ambient light that the UHD52ALV's higher brightness gave it the advantage.

So if you plan to use the projector with a standard screen in relatively bright light, or care most about 1080p SDR image quality, the UHD52ALV has the edge. If you plan to dim the lights, particularly for 4K HDR movie nights, the BenQ TK850 will give you noticeably better image quality for 4K HDR content, which you may consider more important than the slightly lower contrast for 1080p SDR input.

With a Screen Innovations ALR screen, using SI's gray Slate 1.2-gain screen material, the relative strengths of each projector for lights-on viewing shifts slightly. For 1080p SDR content in my tests, the ALR screen closed the gap in contrast between the UHD52ALV and the TK850 significantly for lights-on viewing. And the only difference it made for 4K HDR content was to increase the UHD52ALV's contrast advantage in brighter ambient light.

If you have an ALR screen, in short, and plan to dim or turn off the lights--even occasionally--when watching 4K HDR material, the argument for choosing the TK850 is made even stronger by the smaller difference in contrast at 1080p between the two projectors when used with an ALR screen. For brighter lighting, however, the UHD52ALV still delivered some advantage in my tests for 1080p SDR with an ALR screen, and it also increased its contrast advantage for 4K UHD. So if you expect to dim the lights rarely or never, the UHD52ALV is the obvious choice.

Measurements

Brightness. Using the widest angle setting for the zoom lenses, the measured ANSI lumens for Normal (full power) and Economic modes in each color mode was as follows for each projector:

BenQ TK850 ANSI Lumens

MODE	Normal	Economic
Bright	2544	1359
Living Room	1476	998
Cinema	1542	1042
Sports	1579	1067
Silence	1117	755

Optoma UHD52ALV ANSI Lumens

Mode	Bright	Eco
Bright	2965	1959
Cinema	1820	1225
HDR SIM	1268	826
Game	1576	1031
Reference	691	451
User	1822	1188

Additional key measurements for each projector were as follows:

Measurement	BenQ TK850	Optoma UHD52ALV
Zoom Lens Light Loss	9%	14%
Brightness Uniformity (Wide Zoom)	67%	66%
Brightness Uniformity (Full Telephoto)	67%	72%
Lowest Measured Input Lag (4K)	86.5 ms	Not Available
Lowest Measured Input Lag (1080p)	82-83 ms	75 ms
Fan Noise rating (Normal/Economic)	30dB/28dB	29dB/25dB

Fan noise comparison. The UHD52ALV is rated at a slightly lower decibel level than the TK850 for full power mode, and a significantly lower level for Eco mode, but the general description of their fan noise is identical for both projectors. Both offer the kind of steady sound that tends to fade into the background for anyone who isn't particularly sensitive to noise, particularly in a family room with ambient noise, and both are also quieter when set to Economic mode rather than Normal mode.

With High Altitude mode On, the UHD52ALV has a slight advantage. In Eco mode with High Altitude mode on, those who are particularly sensitive to fan noise may want to apply some form of acoustic isolation, but many people won't find that necessary. In full power mode with High Altitude mode on, most people will want to consider acoustic isolation. With the TK850, High Altitude mode is loud enough that most people will want some form of acoustic isolation with either power mode.

Connections

BenQ TK850:

• HDMI 2.0b (x2, both with HDCP 2.2)
• USB Type A 3.0 (media reader and firmware upgrades)
• USB Type A (power only)
• USB Type Mini B (firmware upgrades)
• DC 12v trigger (3.5mm mini jack)
• Audio out (x2, 3.5mm stereo mini Jack, S/PDIF optical)
• RS-232 (D-sub 9 pin, male; for control)

Optoma UHD52ALV:

• HDMI 2.0b (x2, both with HDCP 2.2)
• VGA in
• USB A (reads files from USB memory; 3.0 to support 4K player)
• USB A 0 (for Alexa/Google Assistant Wi-Fi adapter)
• LAN (network Control, Alexa/Google Assistant, firmware updates)
• 3.5mm stereo in
• 3.5mm stereo out
• S/PDIF optical audio out (2 channel only)
• 12V Trigger
• RS-232 (control)
• USB A (Firmware upgrades/service)
• USB A (for Wi-Fi adapter for PCs and mobile devices)

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