Thursday, October 20, 2005

Sony's Groundbreaking New SXRD RPTVs

The November 2005 issue of Widescreen Review contains a review (download it in PDF form here, if you are logged on to the site) of the hot new KDS-R60XBR1 HDTV from Sony. Sony's first SXRD rear projector, it produces true 1920 x 1080p resolution on a nice, big 60" screen for $5,000. Its little brother, the KDS-R50XBR1, offers 50" of widescreen 1080p resolution for $4,000. There is also a review, not yet online, of the KDS-R60XBR1 in the same month's issue of Home Theater magazine.

SXRD stands for Silicon X-tal (for "Crystal") Reflective Display. It's Sony's own version of LCoS: Liquid Crystal on Silicon, a type of microdisplay which has recently been seen in pricey front projectors but until now not in rear projectors.

As a microdisplay, SXRD creates its image on a small rectangular chip (or actually three of them, one for each primary color) about the size of a postage stamp. This little panel of pixels is made of a liquid crystal material, just as is an LCD (liquid crystal display) chip. But unlike an LCD chip, an LCoS/SXRD chip doesn't transmit light emitted from behind it. The light source instead reflects off an aluminized layer on which the pixels are more tightly squeezed together, to eliminate the so-called "screen door" effect wherein the LCD pixel structure presents itself to the eye.

Because the light passes through the crystal twice, not once, the contrast ratio is vastly improved, resulting in a bright picture with truly dark blacks. The structure of the chip also allows Sony to brag of lickety-split pixel response time, so moving elements of the image don't develop ghost trails.

Sony's LCoS/SXRD rear projectors compete directly with various manufacturers' (Samsung, HP, Mitsubishi) 1080p DLP-based RPs. Those sets use a trick to coax true 1920 x 1080p resolution out of a 960 x 1080p microdisplay chip. Texas Instruments, the originator of DLP, calls it SmoothPicture. Other folks call it "wobulation." A mirror in the projection path is pivoted ever so slightly to shift the image by one pixel horizontally, as each video frame is being projected. (For more on this, see An Eye on DLP, No. 3.) Critics say that produces eye fatigue. Sony's SXRD chips are natively 1920 x 1080, and no such trick is needed.

Bill Cruce's review of the KDS-R60XBR1 in Widescreen Review is a truly glowing one. In terms of picture quality, about the only minor flaw he cites is oversaturated green. Geoffrey Morrison in Home Theater is more guarded with his accolades, mentioning that both red and green were too strong in the unit he reviewed — though they are the correct shades of the respective hues. "So objects may look really green," he says, "but they're not greenish-yellow or greenish-blue like the colors that many digital displays can produce." But: "One side of the screen had a bluish-green tint [on test patterns], while the other side had a reddish-orange tint." The review by Cruce in WR mentions no such anomaly.

However, Morrison also says that he was reviewing was a preproduction model, and that Sony claims the color accuracy will improve in units shipped to stores.

Morrison also found the improvement in picture detail with the KDS-R60XBR1's 1920 x 1080 resolution, compared with a 720p display, no better than "subtle but noticeable." You would expect a bigger jump in apparent resolution, since 1080p more than doubles the number of pixels of 720p. But, though this set has a 1080p display, it can't input a 1080p signal!

That's right — the best signal it can take in is 1080i. Now, I am given to understand that 1080i fare is intentionally filtered to remove about 30% of its vertical resolution, because any "i"-for-interlaced scan will produce an artifact called "line twitter." When a video detail is small enough to occupy just one scan line, every second video "field" will omit it. The detail will accordingly blink on and off! Vertical filtering obviates that, making sure that no detail is so small as to completely disappear every 1/30 second.

So I'll bet Morrison was watching vertically filtered 1080i material (from a D-VHS tape player) scaled to 1080p by the KDS-R60XBR1. That's really not a good way to judge the ultimate picture quality of a 1080p-native display.

But Morrison had little choice, since (a) as yet there exists no 1080p consumer-video source hardware, other than a high-def PC hookup; (b) there is little if any 1080p source material, a situation that will probably change when high-definition DVDs arrive; and (c) the KDS-R60XBR1 can't accept a 1080p input signal anyway. Both reviews mention Sony's reason for omitting the capability: the present lack of an industry standard for copy protecting 1080p input.

I mention this because I think it a good idea for potential buyers of the KDS-R60XBR1 to wait until there is a successor model that does accept 1080p.

The KDS-R60XBR1 has stunning black levels and snappy contrast renditions, both reviewers say. Most HDTVs other than direct-view CRTs have problems rendering deep blacks, and CRTs are usually limited in how bright they can get. The KDS-R60XBR1 can do blacks nearly as well as a CRT (0.006 or 0.007 foot-Lamberts, per HT) and dazzle you with its brightness (93.31 ft-L). That gives a whopping full-on/full-off contrast ratio of fully 13,330:1.

"The best plasma we've measured had a black level of 0.023 ft-L; the best RPTV ... 0.080 ft-L," writes Morrison. "Most of the front projectors we've measured have a higher black level than this 60-inch RPTV. Suffice it to say, I was impressed." Clearly, the Sony SXRD RPTV "out-blacks" any existing DLP RPTV.

Part of the reason for these outstanding numbers is the KDS-R60XBR1's Advanced Iris, which automatically contracts, reducing the amount of light reaching the screen for dark scenes, and then opens up for bright scenes. Morrison says you can just barely detect it working, and if it bothers you you can defeat it by selecting one of six presnt iris levels manually. Even the full-open setting produced an impressive 3,100:1 contrast ratio.

The two reviews seem to disagree about how well the KDS-R60XBR1 does video processing such as deinterlacing and resolution scaling, with the WR reviewer being wholly thumbs-up about it and the HT reviewer noting some flaws. I have no idea why there was a difference in this department.

But on the whole, it seems clear that the initial Sony KDS-RnnXBR1 SXRDs come right out of the starting gate as the RPTVs to compare all others to ... and that's saying quite a lot.


After I wrote the above the Nov. 2005 Sound & Vision arrived, with a review of the Sony 50" SXRD model, the $4,000 KDS-R50XBR1. Al Griffin's opinion was much like those of Bill Cruce and Geoffrey Morrison: "gorgeous picture ... natural color ... deep, CRT-like blacks ... fine resolution."

Griffin also complemented "extensive feature set and picture tweaks, which go well beyond many other televisions." As the lab results and discussion online here mention, "Only minor tweaks using the red, green, and blue gain and bias controls in the set’s Advanced Video menu were needed to get [color temperature] perfect — no service-menu adjustments needed."

Color temperature is supposed to be the same value, 6500K, at all brightness levels. Most TVs don't give you that desired degree of uniformity, giving the picture a blue or red cast instead. Sometimes, there is a different false tint at different brightness levels. Such false tints are most apparent in a black-and-white picture, but also affect color pictures.

The fact that the Sony puts red, green, and blue gain and bias controls in a user-accessible menu is also unusual. RGB gain and bias are the main controls used by a professional calibrator to calibrate color temperature and grayscale. (The latter includes avoiding any green tint, not just red or blue, at the various levels of brightness.)

So the Sony SXRDs let you calibrate them on your own!

The S&V review, like the other two, noted that the Sony doesn't support 1080p HDTV input signals, even though the screen output is always 1080p. The only other minus factor the reviewer cited was the lack of a signal-strength meter to help you tune in over-the-air digital channels. Even so, the Sony pulled in all the reviewer's local stations, including the most troublesome one, without any fuss.

Oh, and the review also chides Sony's remote for not having a backlit keypad. When that's the extent of the negatives, while the positives are so prepossessing, the TV is clearly a big winner.

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