Panasonic PT-AT6000 3D LCD Projector Review

2D Calibration

Note: Our Panasonic PT-AT6000 review sample was calibrated using Calman Professional, the industry-leading video calibration software. These measurements reflect the projector shooting into the lens of our colorimeter.

Greyscale

We investigated most of the picture modes on the PT-AT6000E (quickly passing over the super-bright, accuracy-be-damned ones) and, not surprisingly, picked the Rec709 mode as our starting point, since it was the most accurate out of the box preset. We did also investigate calibrating the Cinema2 mode as part of the process, and found that it had considerably less linear greyscale tracking.

In any case, here is the greyscale performance of the Rec709 mode before calibration. The only setting we adjusted was the [Lamp Power] – the Panasonic PT-AT6000′s images were very bright, and owed to the absence of any sort of manual iris control, the only way of bringing these down was to engage the “Eco” mode (which does change the colour of grey, so choose your preferred mode before any calibration takes place).

Pre-calibration RGB Tracking
Pre-calibration RGB tracking and delta errors (dEs)

In this mode, the PT-AT6000E gave an impressively accurate result which is better than some flat-panel HDTVs, which is not something to be sniffed at considering the comparative complexity of a projector. The image is overall too blue, but not at the level that we feel will significantly detract from the quality of the presentation.

The first control we can use to influence Greyscale is [Colour Temperature], in the main PICTURE menu. Adjusting this allowed us to adjust white point, without sacrificing any light output. That’s great, because it basically gives us a “free start” – not that the PTAT6000 had any difficulty producing a bright image in the first place.

Post-calibration RGB Tracking in [REC 709] mode
Post-calibration RGB tracking and dEs in [REC 709] mode

The [Advanced Menu] features 2-point Greyscale controls, with logically-named “Brightness” and “Contrast” controls for R, G and B (brightness is for the low end, contrast for high). Using these alone left us with fairly linear Greyscale tracking, in the Rec709 mode, that is. We still did have some discolouration at the 5-20% stimulus positions, so we entered Panasonic’s gamma curve editor to sort these out by targeting our adjustments to either the R, G or B curves. In the end, we were left with delta errors below 3 at nearly every point.

Gamma

Pre-calibrated Gamma tracking in [REC 709] mode Post-calibrated Gamma tracking in [REC 709] mode
Pre-calibration gamma tracking (2.2) Post-calibration gamma tracking (2.4)

Out of the box, the Rec709 mode’s gamma tracked linearly (provided the Dynamic Iris system was off), but at 2.2. Even after a few minutes of watching in the dark, before doing any measurements of the projector’s luminance levels, we reached for the remote and dialed this down. 2.2 is a good idea for rooms with a good amount of ambient light, but for a light-treated projection environment, it causes images to appear slightly lacking in depth. In any case, achieving flat 2.4 gamma was no trouble whatsoever – we simply entered the [Gamma Adjustment] menu, and set [Gamma Preset] to “+0.40″.

Gamma menu
Gamma adjustment menu

For the most part, we found the Gamma Adjustment menu to be a dream to use. Pressing the left and right arrow keys lets the calibrator choose a stimulus level to adjust, with up and down raising or lowering the light output. The handiest part is that you can press Enter on the remote to jump between Y, R, G and B, rather than having to back out of the menu and select a different option.

Colour

The colour management system present on the Panasonic PT-AT6000E is… interesting. While by no means a nightmare, it’s less intuitive to work with than nearly any CMS we’ve used on an HDTV, including Panasonic’s. That’s in contrast to the gamma curve editing tool we used above, which we’d be happy to see on a Panasonic plasma.

There are two modes, one of which is “CURSOR”. The idea here is that you use the arrow keys on the remote to manoeuvre a bullseye target over a frozen video frame, hone in on a colour you want to adjust, and then go nuts with the controls. The second is the traditional mode, labelled “RGBCMY”, in which you simply select the colour you want to adjust rather than having to hunt for it. Upon selecting a colour, the video image is frozen, and two boxes appear on screen. One of them apparently represents the colour as it currently stands, the other, the adjusted colour. The calibrator then has to tap the Enter key to un-freeze the image and actually see the result of the adjustment – unlike most colour management systems, the image is not live behind the menu.

Given that this menu design is impractical from the point of view of calibration, we’d guess that it’s been designed for a “tweak by eye” approach and that the boxes were never intended to be measured in the first place (which isn’t easy). Again, from the point of view of accuracy, this serves almost no purpose in high quality projection other than giving the user the apparent satisfaction that they’ve left their mark on the picture. It’s a moot point though, because in our experience, these colour patches aren’t accurate anyway. The image shown in the “after” box especially varies wildly to what the colour is actually like on the live video image!

CMS menu
CMS menu

All of these oddities – especially the bullseye “pick a colour” mode, suggest that the colour management system has been pitched as a “choose the colours that suit your preferences” tool, but fortunately, the CMS is functional and usable underneath this unusual surface. The implementation might make it look like a toy, but it’s not.

In practice, using the CMS on the PT-AT6000 is not as simple as using the CMS on Panasonic plasma or LCD TVs. The controls have some unwanted interaction with each other: for example, the saturation adjustment does affect saturation, but also has a large knock-on effect on luminance (for that reason, we weren’t able to get a completely perfect red). That’s in contrast to the similar controls on Panasonic plasmas, which have almost no overspill. Also, there were cases where we would have found it beneficial to take the controls past the extremes allowed by the menu design.

One last usability quirk: the colour adjustments have to be manually saved before exiting the CMS menu, otherwise they will be lost to the ages. That will come as surprise to anyone who hasn’t calibrated a Panasonic projector before, and if it wasn’t cruel enough, it’s doubly so given that the adjustments made in the Greyscale and Gamma menus do not have this same behaviour, making it totally unexpected. The sadists!

Fortunately, after all this, it’s possible to adjust the controls in a way that results in largely excellent colour reproduction, with all primary and secondary colours on our review sample achieving overall delta errors of less than the “easily visible threshold” of 3. We certainly couldn’t pick out any issues in real-world usage.

Out of the box, colour reproduction was decent, but with an oversaturated green and elevated luminance levels for some of the colours. The oversaturated green is especially strange, causing a misshapen triangle to appear when plotted on a CIE diagram. There’s room for improvement with this, given that the mode is called “Rec709″ and is likely to give enthusiast home cinema users the idea that there are no large inaccuracies relative to the Rec709 HD standard. Hopefully, those same enthusiast users will be the ones having their projectors calibrated so they can see its full performance. For those who aren’t, we’ve seen worse inaccuracies.

Pre-calibration CIE chart in [REC 709] mode
Pre-calibration CIE chart with reference to HD Rec.709
Pre-calibration Luminance levels in [REC 709] mode
Pre-calibration colour luminance (coloured bars = targets; black bars = measured values)

After calibration, we were left only with a slightly desaturated red and blue as the remaining errors, neither of which could be spotted during video footage. While it was possible to fully (or nearly fully) saturate these colours, it would involve having a higher luminance error, which would be a more visible issue.

Post-calibration CIE chart in [REC 709] mode
Post-calibration CIE chart with reference to HD Rec.709
Post-calibration Luminance levels in [REC 709] mode
Post-calibration colour luminance (coloured bars = targets; black bars = measured values)
Colour saturation tracking
Post-calibration colour saturation tracking

One final sticking point on the road to accurate colour reproduction on the Panasonic PT-AT6000E was with the linearity of magenta. During calibration, we made a large offset to this colour’s hue, since it was being tinted blue before calibration. When we measured saturation tracking, though, we could see that with this correction dialled in, the colour was only on target at 100% saturation, careering towards red at its lower points.

We didn’t manage to cure this entirely, but we mitigated the error by adjusting the Hue, Saturation and Luminance controls for magenta in different ways in order to balance the inaccuracies. At one point, we managed to get linear hue and saturation tracking with this colour, but only if we sacrificed a lot of luminance accuracy. The above result presents the best compromise, and viewing of content never gave us any cause for concern.

3D Calibration

We calibrated the tri-dimensional output of the Panasonic PT-AT6000 by attaching the active-shutter glasses to the front of our Klein K-10 colorimeter, activating the glasses and the 3D mode, and once again shooting the output of the projector into the colorimeter’s lens, with the glasses of course adding their own tint to the light path.

After some experimentation, we found ourselves at a crossroads. In terms of a compromise between brightness and accuracy, the “Cinema2″ mode produced a brighter image than the “Rec709″ mode. However, this seems to be partly achieved by an unusual gamma curve (even once the [Dynamic Iris] system is shut off), as well as higher light output. It does also feature highly oversaturated colours, however, although those can be corrected with calibration.

On the other hand, the “Rec709″ mode is a little dimmer, but with this mode, it’s possible to achieve flat gamma tracking. The choice is up to the user – unless you’ve specifically installed a higher gain screen with 3D projection solely in mind, 3D will need all the brightness help it can get, which will probably weight things in favour the less accurate, but brighter “Cinema2″ mode.

For completeness, we also measured the different [3D Eyewear Brightness] settings, to figure out what these did. These affect only the glasses, and do not perform any sort of gamma manipulation in the projector itself. We went for the “Light” setting, for obvious reasons.

3D Mode Greyscale

Pre-calibrated Greyscale in the “Rec709″ mode was tinted red. When we first switched into 3D, the Rec709 mode had new basic settings, with [Contrast], [Brightness] and so on all appearing at their default positions of 0. However, under the surface, the gamma curve and colour management memories we’d created for the 2D mode were still being applied. If you’re calibrating in the third dimension, remember to manually select separate memories for the Gamma and Colour Management settings. We undid these 2D-specific adjustments and ran some measurements to reflect the state of an out-of-the-box Panasonic PT-AT6000 running in 3D Rec709 mode:

3D Pre-calibration RGB Tracking
3D Pre-calibration RGB tracking and delta errors (dEs)

Using the Gamma Curve editor as well as the basic 2-point Greyscale controls, we cleaned up 3D greyscale tracking. We deliberately chose not to correct the linearity issue at 100% stimulus; which results in bright highlights taking on a slight red-green tinge, because this would involve discarding more brightness – and again, in 3D, we need every single lumen we can get. We felt that slightly tinted highlights would be a sacrifice worth having, all things considered.

3D Post-calibration RGB Tracking in [REC 709] mode
3D Post-calibration RGB tracking and dEs in [REC 709] mode

3D Mode Colour

For the benefit of users who don’t have access to 3-D calibration products or services, here is the out-of-the-box colour accuracy in the Rec709 3D mode, which is not too extreme. Once again, there is a strange oversaturation of green, but other colours are more or less on target.

3D Pre-calibration CIE chart in [REC 709] mode
3D Pre-calibration CIE chart with reference to HD Rec.709
3D Pre-calibration Luminance levels in [REC 709] mode
3D Pre-calibration colour luminance (coloured bars = targets; black bars = measured values)

And after calibration, where the process and slight limitations are much the same as in 2D:

3D Post-calibration CIE chart in [REC 709] mode
3D Post-calibration CIE chart with reference to HD Rec.709
3D Post-calibration Luminance levels in [REC 709] mode
3D Post-calibration colour luminance (coloured bars = targets; black bars = measured values)

Benchmark Test Results

Dead pixels None
Panel uniformity Left side greener, right side redder, visible with full grey test screens
Primary chromaticity Good (pre-calibration), Excellent (post-calibration)
Motion resolution (approx.) 350 lines (native), 600 lines (Frame Creation), see notes
Digital noise reduction Defeatable
Sharpness Defeatable
Luma/Chroma bandwidth (2D Blu-ray) Full Luma, Full Chroma
1080p/24 capability No judder in 2D, subtle judder in 3D
Input lag 31ms compared to lag-free CRT
Full 4:4:4 reproduction (PC) No

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