Test Report: Panasonic TC-L55WT50 3D LED LCD HDTV Page 4
Test Bench: Panasonic TC-L55WT50 3D LED LCD HDTV >
In the Custom picture/Warm color temperature mode, the TC-L55WT50 measures slightly cool. After calibration, it tracked D6500 across the entire grayscale range. There is a multi-point grayscale adjustment, but the 2-point version works quite well.
Out of the box, color points were close to the SMPTE specified values. Green is slightly oversaturated and greenish-yellow. Magenta is slightly bluish. Yellow is slightly oversaturated, while blue is slightly undersaturated. After calibration, all color points were pretty much spot-on. Once again, we have a situation here where LED edge-lighting shuts off in the presence of a 0-IRE signal. This makes measuring contrast ratio difficult. Taking the same approach as with the Samsung 55EH6000 I tested in the November issue, I used a custom black pattern with four above-black dots in the corners (to keep the LEDs active). I compared this to black level measurements using patterns from my generator that had large amounts of black, but also other information (like a window or crosshatch patterns). The black level on the Black n’ Dots pattern was ever so slightly lower, indicating some light bleed from the higher average picture level patterns from the test generator. This unorthodox methodology seems to be the best way for me to get accurate contrast ratio measurements from panels that cheat and cut to black.
With the settings I used for most of my subjective evaluation, Panel Brightness High, Backlight 50, I measured 53.85 foot-lamberts (ftL) with a 100-IRE white signal and 0.06 ftL with a 0 IRE-black signal for a contrast ratio of 898:1. With the Panel Brightness set to High and backlight set to 100, I measured 100.5 and 0.12 ftL (838:1).
With the Panel Brightness set to Low and backlight set to 100, I measured 105.5 and 0.12 (879:1). With the backlight at 0, I measured 5.319 and 0.0058 (917:1). Interestingly — and oddly — regular video looked better with the Panel Brightness set to High. (The setting’s description in the menu and both the paper and built-in manuals says just, “Selects different levels of overall panel brightness.”)
With ECO/energy save set to On, the backlight set to 100, and Panel Brightness set to Low, I measured 82.72 and 0.094 (880:1). With all those same settings but the backlight set to 0, I measured the best contrast ratio (970:1), with a white reading of 5.36 ftL and a black level of 0.0058 ftL.