Panasonic TC-65CX400U LCD Ultra HDTV Review Test Bench

Test Bench

Full-On/Full-Off Contrast Ratio: 2,406:1

Measurements were taken with a DVDO AVLab TPG 4K generator, an AV Foundry VideoForge HDTV generator, X-Rite i1Pro2 Enhanced spectroradiometer, Klein K10-A colorimeter, and SpectraCal CalMAN 5 calibration software.

Pre-calibration measurements were of the Cinema preset with default settings, which resulted in a hot peak white reading of 53.2 ft-L and buried shadow detail thanks to a too-low Brightness setting. Post- calibration, in the Cinema preset with Warm color temperature, the peak white set to a more comfortable 38.5 ft-L for dark-room viewing, the Brightness control set to reveal black gradation starting at video level 17, and Dynamic Luminance in its default Off setting, the black level measured 0.016 ft-L for a full-on/full-off contrast ratio of 2,406:1. There were no local-dimming capabilities or backlight adjustments.

Delta E for pre-cal grayscale from 20% to 100% brightness ranged from 4.1 at 90% to a high of 7.2 at 30%. Color point Delta E ranged from a low of 0.9 for green up to 7.0 for blue. Adjusting for the lower peak-white output and appropriate black level, without calibrating grayscale or color points, brought grayscale errors down to an average 4 across the board and a maximum of 4.1 among the color points (for the color blue).

Post-calibration Delta E, following adjustment of grayscale and color points, resulted in grayscale from 20% to 100% ranging from a max of 3.1 at 30% to a low of 0.9 at 100%. Color point Delta E was below 2.35 for all colors but magenta, which measured an error of 4.0 that could not be reigned in due to limitations of the CMS controls.

(Delta E is a figure of merit that indicates how closely a display adheres to the Rec. 709 HD color standard. Levels below 3 are considered visibly indistinguishable from perfect; levels around 4 are very good and acceptable for an inexpensive commercial display.) Viewing angle for the VA-type panel was acceptably wide, showing only subtle loss of contrast on a demanding full-field red pattern at 30 degrees off axis from a distance of 8 feet. Backlight uniformity was outstanding, with no streaking or odd tracking behavior of moving objects, and little detectable haloing seen around bright objects.

The TC-65CX400U failed to pass signals below video level 16 (0% black) or above video level 235 or so (100% white). Video levels can range from 0 to 255, but broadcast standards call for programs to be contained inside the 16-235 window. Displays that clip video below 16 can be more difficult to set black level for using traditional below-black PLUGE patterns, and those that clip above-white may crush detail in bright objects that wander above the 235 ceiling. Though clipping usually has little impact on day-to-day viewing, better displays allow the full signal to pass. Beyond clipping, the set borderline failed the chroma resolution test, a not-uncommon failure. 1080i/1080p scaling was excellent, and evident in the clean Blu-ray disc and broadcast images I observed.—RS


Deus02's picture

After reading several reviews about the newer line of monitors, especially with 4K capability and despite their impressive picture and colors, when it comes to the basic parameters of gray scale, gamma and relative color accuracy, right out of the box, in many respects these newer technological phenoms are not much better than their previous CRT brethren. Hence, to get the most out of the set, a good calibration would still be in order.

I found the same thing with my new LG mid-range LCD LED 4K monitor whereby, with the ability to do my own calibrations, I was able to determine that while the relative gamma standard of around 2.2 in the 0-30 and 80-100 IRE range was OK, anything in between was around 1.6, after awhile, making the set virtually un-watchable. My LG allows a twenty point grayscale and gamma calibration and once I completed that to a 2.2 level up and down the scale, after tweaking the color a bit, the difference in the quality and watchability of the picture was quite remarkable, well worth the time and effort to tune things up properly.

rajaram's picture
siti's picture

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