Note: We asked Aldo to take a fresh look at the results described in this
report by DisplayMate and Insight Media, and to provide his editorial
commentary on the significance.

While it comes as no surprise that LCD displays exhibit noticeable shifts in brightness, contrast, and color performance when viewed off axis, a new report reveals unexpectedly poor results for even "flagship" LCD display models. According to a recently released report jointly produced by DisplayMate Technologies and Insight Media, the level of off-axis color inaccuracy–and its worsening with wide color gamut displays–was a surprise even to experts that observed the test results.

The technical analysis was performed by Dr. Raymond Soneira, President of DisplayMate Technologies. In an interview this weekend with Dr. Soneira, he said that, "The chromaticity shift with angle is objectionable even at ±10 degrees for all of the tested LCDs. Everyone that came to see the shoot–out-including industry experts, manufacturers, engineers, reviewers, journalists and ISF instructors–were shocked at how strong the effect is. Everyone knew there was an effect, but the side-by-side comparison shows how incredibly large it actually is. Even when viewers are seated close together side-by-side, each person will see a different picture with noticeably different coloration on an LCD."

Eight HDTV LCD displays were used in the study, representing five major CE manufacturers (additional plasma monitors were used as references). Also, three of the LCD displays were rated as "flagship" top-of-the line sets. Nonetheless, all the LCDs showed large viewing-angle artifacts, according to the report, with noticeably different coloration in both hue and saturation, as well as variations in contrast and black level. With pure saturated colors, all of the LCDs produced a noticeable color shift at 15 degrees, whereas the performance of the plasma displays was visually indistinguishable from face-on viewing to well beyond 45 degrees.

Most manufacturers publish 176-degree (total) viewing-angle specifications for their units, but these have "absolutely no bearing" on the true acceptable viewing angles, according to the study. What is not appreciated by most consumers is that the angular spec is based on where the contrast ratio falls to a level of 10, hardly an acceptable figure. More realistically, an angle of ±45 degrees may reproduce an acceptable contrast ratio, but only with very bright and saturated colors. Pictures that include a wide range of intensities, hues and saturations will appear "significantly degraded" at much smaller viewing angles, according to the report. Dr. Soneira also found that LCDs with extended color gamuts show additional and much stronger viewing angle artifacts than LCDs with a standard HDTV color gamut, due to the use of color mixtures in the extended gamut primary colors.

Because the results vary with product, it would be interesting to see this kind of testing on a much greater sample size, as well as the correlation with panel technology. An S-IPS panel tested didn’t show a color shift with angle, said Dr. Soneira, but it exhibited a very large increase in black level, which significantly reduces both contrast and color saturation, particularly for dim or dark picture content.

The study implies a number of improvements to the way displays are rated and evaluated. For one, a rating of chromaticity shift with viewing angle would greatly assist in product comparisons, as would a better way to convey the acceptable viewing angle for contrast-ratio performance. Perhaps manufacturers (and reviewers) should publish the contrast ratio at ±45 degrees, or else the angle at which the contrast ratio falls to one-half (or even one-tenth) of the peak on-axis value. Manufacturers would also do well to use these kinds of measurements to improve the performance of their displays, and compete better with plasma on performance, not just price.

For more on the report:
http://www.insightmedia.info/reports/2008lcdbenchmarkdetails.php