DLP vs. LCoS Page 2
UNIFORMITY "Picture uniformity" refers to various criteria that define how well a TV delivers a consistent viewing experience across its entire screen. For example, does the screen have "hot spots" in the middle or corners when showing full frame test patterns that fill it with one color? Does the image bow or slant? Are there motion artifacts of any kind?
The Sony had one distinct advantage here in that, like all LCoS projectors, it uses a separate display chip for each of the red, green, and blue primary colors. The HP, like all DLP rear projectors, uses a single DLP chip and a multi-segment color wheel that can cause rainbow trails to be seen along the edges of objects when the viewer blinks or "strobes" his eyes at just the right moment. Many people never see rainbows, but the simple fact is that LCoS displays don't suffer this problem.
The HP also exhibited a nearly invisible motion artifact we noticed in the Madrid travel piece in which the horizontal mortar lines of a brick building seemed to twitter a bit as the camera panned. It was very subtle and wouldn't be a problem in everyday viewing, but we wondered if it wasn't somehow related to the DLP's wobulation.
On the plus side, the HP offered more uniform color across all areas of its screen, and it had an uncommonly wide viewing angle that the Sony didn't share. Viewing angle is directly affected by the the projection screen, which Sony may have engineered to optimize light output or another characteristic of its LCoS technology at the expense of wider viewing angle. But in the end, the Sony's immunity to rainbows was enough to give the LCoS the nod on picture uniformity.
CONTRAST We've saved contrast for last because it proved to be the category that really set the two TVs apart. Some background: Both sets boast a highly desirable feature - an automatic iris or aperture in the light path that can shut down some light from the projection lamp during dark scenes to allow the TV to achieve a deeper black, and therefore better contrast, more detail in shadows, and punchier-looking colors. Only the Sony's menu allows users some direct control over the iris. The HP's dynamic aperture is turned on for most picture modes, and its setting is optimized by the source material. However, in the Studio mode, which is what we used to achieve a color-temperature closest to the industry-standard gray, the aperture is fixed at a position representing the best compromise between black level and other characteristics.
That in part may have accounted for some of the difference we saw in contrast and black level between these TVs, though probably not all of it. Even with its iris settings adjusted to minimize its effects, the Sony was the clear winner in this area. The HP still offered the more natural and neutral gray and certainly had a bright, punchy picture with excellent blacks - better than that of most other microdisplay TVs we've seen. But the Sony's black was about the purest and deepest we've encountered in a rear projector. For example, a dark bar scene from the DVD of Ed Wood, a black-and-white film, showed gobs of detail in the deep background; distant wall hangings were more clearly visible than on the DLP. Details in dark areas of clothing, such as the weave in the close-up of a deep blue sweater worn in The Matrix Reloaded, were also more evident on the Sony.
BOTTOM LINE In the end, all three of our panelists picked the Sony as their favorite, largely on the strength of its blacks. But we can't say with certainty what that proves about DLP and LCoS. At $3,500, the HP costs fully $1,000 less than the Sony for a similarly-sized TV that competes or excels in virtually every other critical area of picture quality. Could HP (or another DLP maker) start from here and match the Sony's black levels if it had another $1,000 to play with, or just by making factory adjustments to aperture or picture modes? Who knows? But consider this: at this writing, Sound & Vision has tested seven 1080p rear projectors with a mechanical iris: three DLPs (from HP and Mitsubishi) and four LCoS models (from Sony and JVC). All the DLPs produced excellent black levels that were the best we've seen from DLP, but none could match the Sony SXRDs or JVC's 70-inch D-ILA set in this area. We'll leave it to the engineers to tell us why, but for now, this round goes to LCoS.