Panasonic Viera TC-P50G20 Plasma HDTV Panasonic Black Level Update: A Progress Report
In recent months reports have been circulating on Internet tech sites that the black levels on Panasonic plasmas have been increasingthat is, getting worseas more hours accumulate on the sets. In fact, Panasonic itself admitted as much, noting that the sets were designed to increase their drive levels slightly, over time, to compensate for phosphor wear, which typically is at its maximum in the first few hundred hours. But Panasonic also noted that the algorithm that controls this might have been a little aggressive. For its 2010 sets, now in stores, it claims to have made the alterations more gradual.
In our August 2010 issue (about to hit the streets as you read this) we reviewed the new Panasonic TC-P50G20, which resides near the top of the company's 2D lineup. It's an outstanding set at a great price. But while the measured black level was impressive (not yet to Pioneer Kuro standards, but comparable to other recent Panasonic 2D models, which means very good), we were concerned about those reports of progressive black level deterioration. Panasonic agreed to let us hold onto the set to test for this problem over several weeks of use.
We began the test at about 175 hours on the Panasonic's "clock." There is, of course, no clock that times the set's usage, such as you'll find on a video projector. No flat panel we know of has such a feature. The 175 hour start time is a guestimate based on the 100 hours put on the set before we performed any measurements, plus additional time accumulated in the course of the review. The set was fed a mid-brightness full white field, with the same picture settings used in the review (THX Picture mode, adjusted as needed for the best picture, not a showroom Vivid mode), and run 24/7 for four weeks.
After approximately 800 hours of total use to date, the black level on the set remains the same as measured at the 100 hour point; that is, 0.008 foot-Lamberts (with an occasional fluctuation down to 0.007 fL, depending on the black source pattern used for the measurement).
If any corrections have been programmed into the set, they haven't been triggered yet, or occurred before 100 hours, when the first measurements were made. But we plan to keep at it until we accumulate approximately 1500 hours—or over a year's use at 4 hours a day. TJN