- Written by Chris Heinonen and Stephen Hornbrook
- Published on 28 November 2011
The LG PZ550 3D Plasma HDTV On The Bench
LG has been very good about including two ISF Expert modes on their TV that makes calibrating them much easier than many other models. They also include a Picture Wizard that walks the user through setting certain controls (brightness, contrast, sharpness, color, tint) on their own with test patterns and blue-only modes. This will get you closer than you would otherwise be by leaving it at the defaults, but it still doesn’t fully adjust the set.
For the calibration, I used the ISF Expert Mode 1 with 100% windows, and then used Expert Mode 2 with 75% windows. I started with the Warm color temperature, as it was the closest to 6500K, but still measured relatively high in the blue and around 7200K. The LG offers the choice of 2 or 10-point calibration, and after the last LG I used I made sure to start with the 2 point instead of the 10. Once the calibration on these points was done, the tracking of the grayscale was very good across the spectrum except for that spike of blue at 70 IRE. Going to the 10 point might have allowed us to fix this issue, but with our overall dE coming in at 2.6 and only two outliers (40 and 70 IRE), we were overall happy with the grayscale.
This does give me a chance to point out something that LG needs to correct in the future. Their on-screen calibration controls utilize a large, bright box on screen that causes errors in readings. Grayscale and color dE would be 0.5-1.0 different with the menu on the screen compared to when it was off the screen, making it a bit of a pain to get correct readings. Additionally, the menus didn’t remember where you were so you would have to get it close, close the menu, take a new reading, then navigate back in the menu to make a further adjustment if the new reading was off. This makes the process take longer than it should and in ISF Expert modes, I imagine everyone would be OK with small, white on black controls that don’t interfere with your instrument readings.
After the grayscale was dialed in, we went to tweak the color decoding as well. This is another area where I have an issue with LG, and with the ISFccc label. LG provides color and tint controls, which seem to interact with Luminance and Hue, but not with Saturation at all. This 2D CMS lets you make some coarser adjustments to the colors, and in cases where there was a huge error (Magenta with the 75% windows), to dial it back to something respectable. However, it doesn’t give you the precision that you would want in a calibration, and with the ISFccc label I would expect more.
Despite the lack of full CMS controls, we were able to pull down the average dE across the colors from 4.9 to 2.3 with 100% windows, and from 7.5 to 2.1 with 75% windows. The largest error is in blue, which is the most acceptable place for color error. The reason for calibrating with 100% and 75% windows was to see if one provided better results in the end, specifically hoping to eliminate that 70 IRE bump in blue if possible. While the overall averages for color and grayscale look very comparable, when you look at the color saturations, you see that 100% should be your target. All the primaries and secondary’s have very similar dE values no matter which you calibrate for, with blue having a bump at 75% saturation on both. However, Magenta goes from a dE of around 1 at 100% saturation using 100% windows to an error of 14 with 75% windows. As this is the only real change, and it’s for the worse, we would use 100% windows for calibrating this display.
LG provides multiple gamma options, and we were able to dial in the display at an overall gamma of 2.22. This did require going back to the white balance controls to adjust the brightness and contrast, which then affect the gamma for those points, but after doing that the gamma was very good overall. Not perfectly flat, but never dropping below 2.05 or above 2.34 across the full spectrum.
Once calibrated, the LG put out a very nice, natural picture with plenty of pop. I’d consider using the 10 point IRE calibration if you really want to eliminate that bump in blue at 70 IRE, though with the LG menu that interferes with readings, it can take a long time.
Color Space Handling
The LG did an exceptional job with the color space handling tests, passing every one with ease. The LG produced one of the better Luma and Chroma Zone Plate images that I have seen.