LG 55LA7400 3D LCD HDTV Test Bench
Full-On/Full-Off Contrast Ratio: 1,136:1
I initially measured the LG 55LA7400 with its Cinema preset/Warm2 color temperature mode selected. Post-calibration measurements were made in the ISF Expert1 mode with adjustments made for dim room viewing. Because the LG switches off its backlight when faced with displaying a 0-IRE (black) signal, I used a custom test pattern for measurements with a small graphic element located in the corner to trick the set into displaying a 0-IRE full-field pattern. In ISF Expert1 mode with Low LED Dynamic Control selected, black level measured 0.026 foot-lamberts (ft-L) and 29.54 ft-L on a 100-IRE pattern to yield a contrast ratio of 1,136:1. The other two options, Medium and High, yielded largely similar results. With LED Dynamic Control switched to Off, black level measured 0.051 ft-L, and a 100-IRE white pattern measured 29.61 ft-L to yield a native contrast ratio of 581:1. The LG’s contrast measurements are well below what I’ve measured from other recent edge-lit LCD models.
In Cinema mode, the set’s Delta E values, pre-cal gray scale, averaged out to 6.11; post-calibration, it averaged a very respectable (and much improved) 1.21, with a high of 1.87 at 20 percent brightness. (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.)
With its Standard Color Gamut option selected, the Delta E of the set’s color points averaged a very decent 2.5. Post-calibration, it averaged an even more decent 2.0. Gamma in Cinema mode deviated from the 2.2 dim room target at the high end of the range to average out at 2.0, though the lower (darker) steps were fairly linear. With the Gamma preset switched to 2.4, the 55LA7400 measured closer to the target curve, averaging out to 2.3.
Picture uniformity wasn’t great: I noted some screen clouding on low-level full-field test patterns, along with corner spotlights on both test patterns and program material. Off-axis uniformity was excellent, with contrast remaining uniform up to more than 25 degrees off center.
The set easily handled most standard- and high-def film and video deinterlacing tests.—AG