We all know that we're supposed to get our HDTV sets calibrated by an expert if we want them to look their very best. (We also know that we're supposed to floss daily.) But in this era of THX-approved presets and LED-backlit 3D TVs, how much difference does a professional calibration make? I decided to find out for myself with my new LG 60PZ750 plasma TV.
The 60PZ750 is a 60-inch plasma HDTV with THX and ISF (Imaging Science Foundation) certifications, network connectivity, and support for stereoscopic 3D video. It has THX settings for cinema and bright-room modes; I could have just used those settings and been mostly happy. Being a curious geek, however, I wanted to explore the process of calibrating the display.
The set's THX modes are pretty locked in--you can make just a few minor changes. THX works with the TV makers, offering THX certification in an effort to replicate the experience of the video editor’s control booth. Although THX modes mostly work well, rooms differ, lighting is imperfect, and every HDTV's characteristics can change over time.
The ISF modes are quite different, exposing a huge array of individual settings suitable for professional calibration. You can fool around with two-point grayscale calibration, or change the settings for 20 different increments along the IRE scale (with 0 IRE being black and 100 IRE being all white).
As a digital-photography aficionado, I’ve calibrated my own desktop displays, and I could have gone the DIY route with my TV. In fact, I did fool around a bit with the Picture Wizard calibration tool built into the LG set. The Picture Wizard in LG’s higher-end HDTVs does an admirable job of walking you through basic calibration for black and color levels, and it’s a good first-level approximation.
But I decided to bring in a professional to see just how well this particular plasma HDTV could be calibrated. How much does professional calibration cost? How long does the procedure take? What tools are involved? Is calibration worth the investment?
Well, it depends. Are you a serious videophile who wants to watch film and video as the directors envisioned? Or are you a casual viewer of mostly sports, in a bright room? Your viewing habits and interests will help determine whether you’re a good candidate for professional calibration.
Consulting a Pro
Ideally, you don’t want to calibrate a brand-new HDTV out of the box--you want the unit to “settle in.” Depending on the display, the amount of time can range from 50 to 200 hours of use. I set up my LG 60PZ750 in the family room, and we watched shows for several weeks prior to scheduling calibration.
I selected Robert Heron to calibrate the HDTV. You may know Heron from HD Nation, Tekzilla, and other Web-video tech shows; he has also written tech articles for a number of publications. He builds his own gaming rigs, and is a general all-around tech nerd.
Heron is also a hard-core videophile who has gone through all the training and certifications for calibrating HDTVs, including both THX and ISF training classes. On occasion he consults for HDTV panel manufacturers and resellers. I’ve watched both his knowledge and his passion for video grow exponentially since he first started reviewing HDTVs. For calibrating a single LCD or plasma HDTV, he charges $350.
Interestingly, I didn’t have to prepare the room at all. My family room can be fairly bright throughout the day, because one wall has an 8-foot glass patio door. Although blinds cover the glass door, they aren't enough to block the light entirely. Light leakage wouldn’t be an issue during the calibration, however, since the sensor Heron normally uses stays close to the HDTV.
Heron arrived with a rolling cart full of gear, but for the most part he used this sensor.
The X-Rite i1Pro is a spectrophotometer that’s a little slow but mounts against the display, minimizing the effect of stray light.
Heron uses SpectraCal’s CalMAN version 4 for collecting and analyzing data from the i1Pro.
One of the problems that have traditionally plagued HDTV calibration is the difficulty of accessing all the color-management tools built into the TV itself. In older HDTVs, these settings were often called the “factory” or “service” menus, and were accessible only if you pressed a special key sequence on the remote.
However, the 60PZ750 has full ISF support, which exposes the HDTV's color management system. The CMS contains highly granular controls, with individual adjustments for both primary and secondary colors, as well as for tint and contrast.
Calibration consists of taking measurements with the sensor, capturing them on a PC running CalMAN, and determining how closely the measured settings adhere to the ideal. For example, the ideal grayscale color temperature is D6500 (6500 kelvins) across all grayscale levels, from 10 percent to 100 percent, for each color.
Initial Tweaks and Color Management
Before we dove into the intricacies of the color management system, however, we checked out the basic settings. Depending on your HDTV, you may not need fancy tools or software. The Picture Wizard in the LG HDTV, for example, offered an easy way to eyeball fundamental settings such as sharpness levels.
Heron also collected the results for the THX Bright Room setting I’d been using to break in the plasma set. We used this figure as a reference, since it’s a fixed setting. The color temperature actually was close to the desired D6500 (maybe a bit high, toward D6700). The color balance wasn’t perfect, though.
Each set of three bars represents various RGB settings at IRE ranging from 20 to 100. You want all those bars to be flat at the 100 mark on the Y-axis for each of the IRE settings. In the results shown here, green seems a little low, while blue and red are a bit high, on average.
The gamma was a little off--but then again, that was no surprise with a fixed setting tuned for brightly lit rooms.
Once we had collected the precalibration data, the next move was to change the menu settings from THX Bright Room to ISF mode 1, giving Heron access to all the settings, including the color management system.
The first calibration step was to tune the gamma. Dialing it to the 2.2 setting took only about 15 minutes; in fact, the ISF mode 1 “warm” setting was already pretty close. Heron also tweaked the grayscale tracking at this point.
Next, we started tuning individual levels for each primary and secondary color. This is where the process got repetitious. After we spent several hours tweaking each individual primary and second color, the final tuning looked like this.
It’s not perfect, but you never hit perfection--you just get as close as you can across the IRE range. One reason you can’t reach perfection is the interaction between settings: For instance, we’d tune the settings at IRE 90 and hit near-perfection, only to find out that the color balance at IRE 70 had shifted way out of whack. What we ended up with represented the best compromise we could reach.
If you look at the CIE chart at the lower left of the screenshot above, you’ll see that we nailed the colors fairly closely. All in all, it looks pretty good.
The Numbers Aren't the Only Concern
It’s possible to get a seemingly perfect set of numbers for most of the settings, and then discover that the actual image quality isn’t what you expect. Each person’s eye and brain differ in visual acuity and perception, and what may seem ideal in the lab might look harsh or off to your eye. In fact, when I first fired up my LG plasma, I thought it looked too “warm,” but I was coming from a rear-projection LCoS unit, which was in actuality too blue.
The visual quality differences I now perceive, after my set's calibration, are somewhat subtle. Dark areas of a scene certainly have better detail, and colors seem natural. If I shift between the THX Cinema and ISF 1 settings, I don’t see huge differences, though I tend to prefer the calibrated ISF 1 setting by a hair. On the other hand, the difference between THX Bright Room and ISF 1 is noticeable, and in that comparison I definitely prefer the calibrated setting.
Is calibration worth the cost and time? In my case, it’s still a little early to tell, but once again it depends on your viewing habits and your eye. Robert Heron will be dropping by my place for a follow-up session after doing some digging to tweak some of the settings further. Maybe we’ll get my HDTV even closer to perfect.