Panasonic TC-P55VT30 3D Plasma HDTV Page 2
The gamma is fixed in all Picture modes except Custom, where the Pro menu offers several fixed gamma options. In addition, the VT30 also provides a Gamma detail-adjustment control that can tweak the gamma into submission at each 10-IRE step of the brightness range up to a maximum of 100 IRE. This lets a skilled calibrator fine-tune the gamma, but it's a tedious process that requires more than a casual familiarity with the mathematics of exponents and an appropriate calculator.
Initially, the Custom mode's enticing adjustments and the potential for separate calibrations for 2D and 3D lured me in, but this proved to be a mixed blessing. I could regale you with the contents of 50-plus pages of calibration notes (I write large) accumulated over several days of multiple setup attempts. But I'll try to be a little more concise.
Gamma affects the brightness in the mid-brightness region. The most commonly recommended playback gamma hovers around 2.2. But, as measured, the gamma options available in the Custom mode's Pro menu were questionable if you want an accurate reproduction of the source. Even the highest available gamma setting (2.6) measured below 1.7 in 2D, and at some brightness levels in some settings, it clocked in at under 1.0. The Custom mode's 3D gammas were slightly better up to 70 IRE, but they still measured nowhere near the numbers indicated by their settings.
As noted above, the VT30 offers a control that can tweak the gamma into more suitable shape. But when I performed a full 2D calibration on the VT30, spending hours tweaking the gamma to just below 2.2 and dialing in the color tracking and color gamut (including the intensity/brightness of each color), the result looked terrible—dark, crushed, and oversaturated.
I abandoned further attempts to use the Custom mode for 2D. Fortunately, calibration in the Cinema and/or THX modes, as performed in the service menu, was good to excellent. The 2D color points were also virtually spot on, although in all cases, the intensity/brightness of the individual colors measured higher than optimum. Turning down the Color control helped, but since it affects all colors simultaneously, it couldn't precisely correct all of them.
The calibrated Cinema mode produced good gamma results in the VT30. The calibrated THX mode worked nearly as well as Cinema, but the Cinema mode's gamma was a bit closer to the ideal 2.2. 2D images looked more fully saturated and three-dimensional in Cinema than in THX, though these differences were subtle. I'm talking about the illusion of three dimensions in 2D playback here, not the use of the set's 2D-to-3D conversion feature. Properly set up, a good HDTV is inherently capable of producing a believable sensation of depth from 2D sources—something we seem to have forgotten in the race to 3D nirvana.
I also noted that after I made adjustments in the service menu, the measured results in normal operating mode were sometimes different. These differences were These differences were minor and acceptable on the VT30.
Apart from having to do calibrations in the service menu, there were no downsides to using the calibrated Cinema or calibrated THX Picture modes for 2D. But Cinema and THX don't offer the ability to do separate calibrations for 2D and 3D, even in the service menu, which defaults to 2D as soon as you open it. Custom mode, which does offer separate calibration controls for 3D in the user menu, suffered from the low gammas I mentioned earlier. However, while these were a bad bargain for 2D, I found that they produced a noticeably brighter, punchier 3D image than either Cinema or THX. A low gamma enhances 3D brightness, a benefit for plasma technology, which has less inherent brightness than LCD.
Oddly, while the 2.6 gamma setting in 3D measured closer to 2.2 across most of the brightness range, that setting (and 2.4 as well) looked dark and gloomy. For reasons that remain puzzling, the lower gamma settings—2.0 or 2.2, which actually measured far lower than that—looked much better. These gamma settings appear to have been cannily crafted to add significant brightness without washing out the picture or producing any other visible, distracting artifacts.