HDTV

Toshiba 55ZL2 4K LCD 3D Display

ARTICLE INDEX

The Toshiba 55ZL2 Bench Test Measurements

The color gamut seems to be slightly off from the recommended REC709 measurements. I would expect this from a new type of panel, in fact it is surprising they got as far as they did.

Toshiba has a few interesting picture modes. Autoview adjusts the backlight based on the surrounding light and the content itself (bright vs. dark). This works quite well, but I did notice fluctuations as it changed.

Hollywood day and night are supposed to be ISF style calibration levels. It gets 6228 degrees Kelvin and a high 2.7 Gamma at Hollywood night mode.

A setting of static gamma of +10 moves us to 2.24 – a much more agreeable gamma setting. You will likely want a slightly higher value than that (which means a static gamma setting of between +5 and+10 depending on your room and preferences).

Color temperature is pretty stable. The Hollywood day/night settings do not get enough red, and green seems to be unusually bright.

The 55ZL2 has a Hollywood Pro mode. With an additional tristimulus USB sensor (I did not get one, so could not verify), the display apparently can calibrate its own gamma, gray level, and primary colors!

Each of these options can also be done manually. This is one of the most extensive CMS systems I've seen so far.

If you have the USB calibration sensor, you can choose an automatic Gamma calibration – you specify what gamma you want (2.4 is the default), and it scans through its own IRE test patterns and fixes both gamma and white balance automatically. Alternatively, you can white balance the display to D65 using 10 or 2 points, using either built in IRE window patterns or your own content.

Finally, primary colors can be adjusted manually or automatically (using the sensor). Secondary colors do not have their own controls.

For those who like the built in settings, Color temperature level 3 comes closest to the 6500K target.

One serious drawback to the 55ZL2 is its backlight. The display uses edge mounted LEDs that reach 400 cd/m2 (less than the 700 cd/m2 that the manufacturer boasts about). The screen is very thin, which leaves a very thin area for the backlight diffuser. This means that the backlights areas are visible when a uniform IRE100 is displayed. The display reaches a 71% uniformity level – something that really needs addressing by Toshiba.

The panel's contrast ratio was measured at 7500:1, I checked this twice. This is much higher than I expected, particularly given this high resolution panel. It looks like the panel Toshiba commissioned (apparently manufactured by LG) is top notch. The panel has no angular artifacts – no serious discoloration or loss of light at side angles or up/down angles that I could see.

The display's spectral footprint is pretty standard:

The artifact testing worked remarkably well, save for a few interesting tidbits. First, when sharpness is set to 0, there is still some image processing at play. To turn off sharpness artifacts, I recommend to keep the sharpness value slightly below at around -10.

The S&M jaggie test went remarkably well, almost no jaggies except for nearly horizontal angles.

One strange test that failed was the chroma burst which failed only on RGB mode. Luma burst failed on all 3 modes.

Another failure was the vertical mixed content pattern: rolling credits at the end of the movie flickered, while the background video stuttered in trying to cope.

BTB, WTW and pulldown testing worked fine. Most modern displays fail to show 1080p on a moving zone pattern with their intermediate frame algorithm turned on. The 55ZL2 did show such artifacts when the Active Vision 800Hz was set to "Smooth" mode. However, in "Standard" mode (which means it does create intermediate frames, just not as many), there were no such patterns.

It's hard to judge the upscaling capabilities of the 55ZL2. Since it has to upscale to four times as many pixels, there's really not enough of a reference point to know if it does a good job at it. I would say that it does seem as sharp or sharper than what typical 1080p screens do these days. I would expect that when 4K video processors come out, we'll be blown away again by how much external processors can improve on scaling.