Having It Both Ways

Responding to the viewing mode selected, the HP xp8020 slides one of its two color wheels into position in front of the light path.

Manufacturers of single-chip DLP projectors have a choice: good color or high brightness and contrast. It's really a choice of color wheels, and it's the downside to Texas Instruments' push toward impressive product specification numbers. The result is an industry that produces (portable and smaller-sized) projectors that target either the business presentation market or video and home theater use — but rarely both.

With its xp8000 series projectors, HP eschews the choice altogether. HP has put two color wheels in a single projector chassis, physically shifting one of them into position depending on the viewing mode. It's a clever idea and one that offers a uniquely direct comparison of the two DLP approaches. Of course, whether it makes for a perfect jack-of-all-trades projector or the master of neither depends on the implementation, but there's no denying the appeal.

In order to achieve DLP's impressive high-lumen, high-contrast technical specifications, most presentation projectors use a color wheel with a clear white segment in addition to the red, green, and blue color-producing sections of the wheel. It's easiest to imagine a wheel with four equal quarters, although variations do occur. Some projector makers actually increase the white segment to more than one quarter of the wheel in order to maximize brightness or contrast specifications. HP itself offers a presentation projector, the mp3220, with an extra yellow segment in its color wheel (in addition to a clear segment) that reduces the red, green, and blue segments to about 60 percent. The higher brightness gained from a large white segment, and in that case the yellow as well, is great for business presentations and graphics that might need to cut through the ambient light of a sunlit conference room.

However, adding bright white light to any image has the obvious effect of washing out colors, much like ambient sunlight used to do — so visibly — back in the days when projectors stretched to achieve even 500 lumens. Admittedly, this clean segment's washing out is much more controlled and directed to individual pixels, so it's not as obvious to the casual viewer. Indeed, since our eyes are inherently more sensitive to luminance variations than to color, it's a reasonable tradeoff, especially if you're reading charts, text, and numbers. It's also nothing new, and Video Systems has written about it in many projector reviews.

HP, however, thinks a projector can do both luminance and color well, and so has given the xp8020 both that standard four-segment color wheel (R, G, B, white) and a six-segment color wheel (equal sections of R, G, B, R, G, B) typical of home theater models. The two color wheels are mounted side-by-side on an actuator that slides one or the other into the light path. The switch, which takes about five seconds, gives the xp8020 either the higher brightness and contrast for slides and spreadsheets or the rich colors that make video more appealing. Interestingly, a third mode, Super Bright, stops the actuator halfway between the two color wheels for very bright grayscale-only viewing.

HP's xp8020 ($4,999), the second generation of its dual color wheel design, comes in a boxy but natty retro-style chassis, with a big, comfortable handle along the right side that's reminiscent of when the unit's 13.4lbs. actually made a projector highly portable. That weight spec isn't really considered that portable today amid the ultra- and microportables, but it's not surprising — it's the testing ground chassis for new color wheel technology. Arguably, 7lbs-9lbs. might be a more appropriate form factor for a projector designed to be so agile in terms of displaying different types of content.

In the xp8020, HP tries to balance portable and fixed-install needs. The XGA-resolution xp8020 has a fixed-install array of connection options on the rear panel, including 2X 15-pin VGA inputs, BNCs, an M1-DA, and RCA YPbPr component. There are also USB, RS-232, and wired remote plugs for control, and even Ethernet for remote administrative control of the projector. On the other hand, the standard 2.0-2.4:1 lens (1.67-2.0:1 short-throw and 2.4-2.88:1 long-throw lens are optional) has manual zoom and focus — less common today for a 13lb. unit, although it helps keep the cost lower.

Similarly, the remote control is more of a presenter's remote, with menu access and navigation controls smartly hidden behind a sliding cover, but it lacks any dedicated controls for volume, keystone, and, most surprisingly for a model designed for different sources, aspect ratio. Any of those require drilling down into the menus, and that's clunky for an otherwise versatile projector. (Incidentally, the menus do benefit greatly from HP's computer UI experience; they are about as intuitive as you'll find in any display.)

Dual color wheel technology gives the HP xp8020 both the high brightness and contrast for which DLP has gained a reputation and the accurate color of a video-oriented home theater projector.

When I tested the xp8020 I measured 4140 ANSI lumens in that Super Bright mode, and that's actually higher than HP claims. In the Business Graphics mode, my meter readings averaged 2721 lumens across the entire image, and that's a little more than 10 percent lower than HP's number (a fairly common industry differential), but still very good for the weight and price. My brightness measurement for Theater mode was only 830 lumens, but that's ideal for a controlled video-viewing environment.

My contrast ratio measurements were good, too, especially with a 488:1 ANSI checkerboard ratio in Business Graphics mode. Although those basic numbers are good, my test unit did have a problem with brightness uniformity, with a 30 percent differential between the lower half of the image and the top half.

Color performance was mixed, and maybe that's no surprise. According to my ColorFacts test equipment, in Theater Mode the primary and secondary colors were almost right on, if a little weaker than ideal on blue and a little stronger on green. In Business Graphics mode, as if to accentuate the difference, colors were noticeably less accurate even to the naked eye. Yellow in the SMPTE bars was almost the same color as the cyan, and magenta leaned heavily toward blue. Green was much weaker overall. And not surprisingly, the grayscale range in the Business Graphics mode was also severely clipped on both the bright and dark ends. Theater and Super Bright mode grayscale ranges were better.

For all the versatility of the two color wheels, there are a few shortcomings in video mode that suggest HP's xp8020 still focuses more on business usage than straight video. For example, the xp8020 I tested had a hard time with scaling fine resolutions, as with any 1×1 on/offline sequence from my Extron VTG-400 test pattern generator, particularly on 720p. Those are solvable problems with greater attention to engineering in HDTV modes, although improvements to scaling and other components may increase the unit's cost of goods sold.

Even though the xp8020 is a second-generation model of the dual color wheel, HP is still trying to find the right balance between larger fixed-install projectors, which generally have more cooling capacity and brighter lamps and thus fewer color compromises, and portable form factors. Ultimately, the latter might be a more appealing solution in the long run because small size would simply add to the versatility.

Still, the HP xp8020 delivers a good value for a $4,999 price that essentially doesn't demand much of any premium for the dual color wheel technology. More importantly, the dual color wheel is extremely promising because it proves that the DLP color/brightness tradeoff isn't written in stone.

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