BenQ TH670 is an inexpensive, crossover 1080p projector for home and office. The banner at the top of BenQ’s TH670 webpage reads “Home Entertainment Projector,” and some features–notably full 3D support and a fast lag time for gaming–aren’t of much interest for office use. But the model name shows up on both the Home Theater and Business lists on BenQ’s website, and the projector can do a credible job in either role.
The 1080p resolution and 3000 lumen rating are appropriate for presentations with fine detail in a mid-size conference room and for HD video that can stand up to ambient light in a family room. More important is that the TH670 delivers suitable image quality for both applications, which isn’t true for much of the competition. Most DLP models are tweaked to show fewer rainbow artifacts for either data images or video, for example, depending on what the model is meant for. The TH670 shows very few of these artifacts with either kind of image.
Color Preset Modes. The TH670 offers four customizable color modes: Bright, Vivid, Cinema, and Game. In addition, there are two User modes, which you can rename, so you don’t have to remember which one is meant for what.
As a practical matter, for business presentations and other data images, Vivid, Cinema, and Game modes all deliver well-saturated, suitably eye-catching color. For video and photos, Bright mode has an obvious green bias, as is typical for the brightest modes in many projectors. Color in the other three modes is more than acceptable overall, but a bit short of excellent.
In a direct comparison with the calibrated projector we use as a reference, it’s easy to see that the TH670’s colors are a little dull and dark in all modes. Without side-by-side images, however, colors look obviously dark only in Bright mode. Whether you’ll notice the issue in other modes will depend on how well-trained an eye you have. However, a minor loss of color fidelity is forgivable for such an inexpensive projector. Color balance is excellent in all modes, with neutral grays at all levels from black to white.
Data Presentations. Not all 1080p projectors hold detail equally well. The TH670 does swimmingly on this score. White text on black, for example, was easily readable at 6 points in my tests and black text on white was easily readable at 5 points. It also does an excellent job of resisting pixel jitter and moire patterns on images that tend to bring both out. Results can vary depending on your graphics card, but in my tests, the image was as rock solid with a VGA connection as with HDMI.
2D Video. Handling detail well is an obvious benefit for HD video too. In addition, the test unit did a good job of avoiding posterization and holding shadow detail, even on our most demanding test clips. I saw some noise, but less that with many models in higher price ranges and only in scenes that tend to cause it. Contrast ratio is a bit low, but it’s obvious only in theater dark lighting. With ambient light in a family room, the benefits of a higher contrast ratio tend to get washed out in any case.
I ran into one odd behavior when I was connected to a Blu-ray player as opposed to a PC or FiOS. Every time I started playing a DVD or Blu-ray disc, the TH670 switched to Bright mode, forcing me to reset it to the mode I wanted. BenQ insists this is by design, but it’s hard to understand why, considering that all of the other modes offer better color quality. In any case, if you want to use one of the other modes, you’ll have to switch to it every time you start a movie.
3D video offers essentially the same quality as 2D in most ways, but with only one color preset. It also does well on those aspects of image quality specific to 3D. I didn’t see any crosstalk and saw just a hint of 3D-related motion artifacts in the most demanding clips.
Rainbow artifacts are a minor issue at worst for the TH670. With data images, the only time I saw any was with one test image that’s designed to make them show. With video, I saw some with clips that tend to bring them out, but less often than with many home entertainment projectors. Anyone who sees these artifacts easily will see them with the TH670, but infrequently enough with most material that it’s unlikely to be annoying. The potential exception is with black-and-white input, where they show more often.
Zoom. The 1.2x zoom offers some flexibility for how far you can position the projector from the screen for a given size image.
Small and lightweight. The TH670 measures 5.4″ by 12.9″ by 9.2″ (HWD), and it weighs only 6.6 pounds, making it small and light enough to carry with you or set it up quickly as needed if you don’t have a place to install it permanently. The optional carrying case is $39.
Useful audio. The built-in 10-watt mono speaker offers usable sound quality and enough volume to fill a typical family room or medium-size conference room.
Full HD 3D. The TH670 offers full HD 3D compatibility, and automatically switches to and from 3D mode as needed. The 3D works with DLP-Link glasses only.
Good Lag time. The 33.1 ms lag time in Game and Bright modes is at least a match for the vast majority of projectors and faster than most.
Security. The menu offers password protection. There’s also a Kensington lock slot on the back and a security bar along the left side.
Warranty. The price includes a one-year warranty for parts and labor and a 90-day warranty for the lamp.
BenQ TH670 Rear Connection Panel
Brightness. Using Normal lamp mode, we measured the sample unit that BenQ provided for testing at 93% of its 3,000-lumen rating for its Bright color preset and at 38% to 53% of its rating with its other presets. With Economic lamp mode, the measured brightness dropped by about 20% for each preset mode.
With the zoom lens at its widest angle setting (the shortest throw for the image size), we measured the ANSI Lumens for Normal and Economic lamp settings as follows:
BenQ TH670 ANSI Lumens
In addition, there’s a SmartEco mode that BenQ says works much like an auto iris, making dark scenes darker. However it changes brightness by lowering lamp power, which conserves energy and lengthens lamp life.
Zoom Lens Effect. With only a 1.2x zoom, the zoom setting has little effect on brightness.
Brightness uniformity. The TH670’s measured brightness uniformity is remarkably low, at only 50%, making variations easy to see with a solid white image. With the test unit on a table in front of the screen, the bottom of the image was brighter than the top, and the center vertical section brighter than the left or right sides. However, the brightest and least bright areas are far enough apart, and the change is gradual enough going across the screen, that the variation isn’t much of an issue. Break up the field of view with any image–whether graphics, text, video, or a photo–and the difference is hard to see even if you look for it.
Color brightness. We measured the color brightness for the TH670’s Bright mode at 20% of its white brightness–a big enough difference to explain why colors are noticeably dark in that mode. With the three other presets, the color brightness is closer to white brightness, at 37% for Vivid mode, 44% for Game mode, and 60% for Cinema mode, which is consistent with Cinema mode offering the best color quality. The low level of color brightness compared with white brightness in all modes means full color images won’t be as bright as you would expect from the 3000-lumen rating.
Rainbow artifacts show often enough that anyone who sees them easily will notice them, but infrequently enough that few people will consider them a problem, with the possible exception of black and white video, which tends to show the artifacts more often.
Fan noise. Rated at only 31 dB in Normal mode, this projector has a steady whooshing quality that I don’t find distracting. It’s also quiet enough that I wouldn’t notice it from even three feet away unless I listened for it. If noise is one of your pet peeves, however, you’ll probably want to sit farther away. In Economic mode, the rating is an even quieter 29 dB, but I couldn’t hear much of a difference.
BenQ recommends the High Altitude mode for a 1500 to 3,000 meter (4921 to 9843 foot) altitude. As with most projectors, the noise level isn’t rated. However, it’s easily noticeable from 20′ away, with sound quality that’s more of a hair-dryer hum than a whoosh. Here again, there’s almost no difference between Normal and Economic modes. If I were using the TH670 in high altitude mode, I wouldn’t want to sit much closer than 20′. If you’re sensitive to fan noise, you won’t want to sit even that close.
Input lag. Measured by the Bodnar meter, lag ranges from 33.1 ms in Game mode to 33.9 ms in Cinema mode with default settings. Turning off Brilliant Color raises the time to a still low 35.2 ms in all modes.
Lamp life. The lamp is rated at 4,000 hours in Normal mode, 6000 hours in Economic mode, and up to 10,000 hours in SmartEco mode. Keep in mind that the 10,000 hour rating is based on best-case assumptions, so it isn’t likely you’ll see that long a lamp life in real-world use.
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