4K TV Reviews

Pre-calibration measurements were made in the Calibrated Dark preset at the default settings. Post-calibration measurements were made with the same preset active. With the P652ui-B2’s Active LED Zones switched on, its black level measured 0.002 ft-L and peak white 35.9 for a contrast ratio of 17,950:1. Measurements were approximately the same for all Black Detail presets. With Active LED Zones off, black level measured 0.009 ft-L and peak white 31.6 ft-L for a contrast ratio of 3,511:1.

PRE-CALIBRATION

POST CALIBRATION

While these numbers are good overall, note that contrast ratio for Vizio’s 2014 M Series HDTV measured twice as high, though black uniformity with that set wasn’t nearly as good as with the P652ui-B2.

The Delta E of the Vizio’s pre-cal grayscale averaged out to 9.1; calibration improved that to a 5.5 average, with a high of 13.5 at 100 percent brightness. The average was skewed by grayscale nonlinearity at the high end; otherwise tracking was mostly smooth. (Delta E is a figure of merit that indicates how closely a display adheres to the Rec. 709 HD color standard. Experts generally agree that levels below 3 are visibly indistinguishable from perfect color tracking.)

The Delta E of the Vizio’s color points at the Calibrated Dark mode’s default settings averaged a not-great 5.8. Calibration improved things a bit to 3.6.

With Active LED Zones turned on and the 2.4 Gamma preset selected, gamma in the Calibrated Dark mode averaged 1.6, measuring 1.5 for most of the IRE range and hitting 2.2 at 100%. Calibration improved things to 1.9, hitting 1.7 at 70%, and 2.4 at 90%.

Full-field gray test patterns appeared even when viewed straight on. I did see some uniformity issues when displaying a 0% (black) pattern, but they weren’t visible when watching regular program material.

Off-axis performance was about average, with contrast and color starting to fade when viewing about 20 degrees off from center-screen.

The Vizio passed most of our standard- and high-def video processing tests with the exception of 3:2 HD pulldown. It also failed our Video Clipping test, which checks to see if below-black and above-white information in the video signal can be displayed. Although television images are theoretically not supposed to contain below black or above white information, programming does sometimes contain above-white information. Clipping above-white, specifically can show up as poor detail in white highlights—an issue I regularly observed when watching movies on the Vizio.—AG