I wish I could say I had some clever reason for reviewing two nearly identical plasmas. Perhaps there was, but it's lost to me now. A few months ago, Panasonic asked me if I wanted to review the TH-50PZ700U, so I said sure. Then, a month or so later, they asked me if I wanted to review the TH-42PZ700U, so I said sure. It's not all magic here, folks. Sometimes this kind of excitement just happens.

But then I got to thinking. This would be a great time to, yet again, be ignored about how you don't need 1080p in a 42-inch screen size. Not to sound biased against the little ones, but physics, physiology, and math all pretty well back me up on this. So what the hay (or "heck," if you prefer—God forbid I should say #@%%). Let's see what we can see.

Aww, It's Wee
There was a time when all of us would have marveled at a flat, 42-inch display. I guess I'm getting jaded, because it seems pretty small now, especially next to an otherwise identical-looking 50-inch set. They're so identical that you can assume that I'm talking about both, unless I say otherwise.

The glossy black finish looks more upscale than Panasonics have in the past. The back panel has all the jacks you'd want, and, thankfully, they're not set vertically like on many recent plasmas and LCDs. In some installations, vertical jacks may be easier, but, for everyone else, they're a real hassle.

The remote follows the big-button approach that Panasonic has been producing lately. It looks a little silly, but I guess it's easier to read. Perhaps if it were backlit at all, it would be easier to navigate without the big lettering. There's also no direct input access, but the input button pulls up a list where you can select the input you want. The silk-screening looks like you could peel it off with your fingernail. I attempted this without success.

The colorful menus are easy to navigate. When you make an adjustment, the menu falls away, but it comes back way too quickly, making it difficult to check your setup.

The Process
The pair of plasmas will accept 1080p/60 over HDMI but not over component. The PC input disappointingly maxes out at 1,280 by 1,024. They will display a partial image if you feed them 1080p/24. Partial, as in the top left 80 percent of the screen shows an image with big black boxes on the left and bottom. In other words, it doesn't accept 1080p/24, but it sure seems like it really wants to.

Both sets correctly deinterlace 1080i, but neither picks up the 3:2 sequence in a 1080i signal.

With the Silicon Optix Benchmark DVD, the TH-42PZ700U starts showing jagged edges in the rotating-bar pattern very early on, much higher than most displays we've reviewed recently. Its bigger brother does the same, but the jaggies are somewhat less noticeable. Also interesting was a green trail to the bar, which is presumably some lag in the green phosphors. Both panels exhibited this artifact, but the 50-inch a little less so. It's doubtful that you'd see this in most regular video content. With the waving-flag pattern, neither handled video processing very well, with many small jagged edges to the flag. Again, the 50-inch seemed just slightly better here, too. Both are also a little slow to pick up the 3:2 with 480i, although both do it eventually. All in all, you should expect to pair either of these plasmas with a good upconverting DVD player.

With the ubiquitous Fifth Element DVD, the 42-inch showed an abundance of jagged edges and extraneous noise, some of which looked like mosquito noise (which isn't on this disc). Most of this went away when I enabled all three of the noise-reduction options in the menu, and they improved the image considerably. That isn't to say they made it look good; they simply took out what the plasma seemed to otherwise add on its own. The noise reduction seemed to soften the image slightly, but it wasn't overly sharp to begin with on DVD. So this wasn't a big loss. The 50-inch fared a little better with the same overall complaints, but to a lesser degree.

My assumption was that the insides of these two displays would be the same, but, for whatever reason, they seem to be slightly different. Could it be unit-to-unit variation, different tweakings inside the set, more or less pixie dust? I have no way to say. There is still an undeniable family resemblance in the processing.

Similar, but Different
Keeping with the family-resemblance theme, the panels perform pretty similarly on the measurement front. Keep in mind that, despite aesthetic resemblance, the same resolution, and even the same model line, these two plasmas have different glass. This is because you wouldn't be able to fit two million pixels of the size of those on the 50-inch into the smaller screen area of the 42-inch. Knowing this, certain aspects start to become more interesting.

For one, check out the color points. Red and green are both oversaturated, which is pretty typical for flat panels. It seems like a conscious choice, as the two plasmas are nearly identical. Most likely, this is due to the fact that both panels use the same phosphors. This in itself is interesting, as the smaller pixels in the 42-inch would need to be able to produce more light in order to keep the overall light output up. Which came first, the efficient phosphors in the 50-inch size that allowed the 42-inch, or development of new phosphors that would work in the 42-inch and then used in other panels? Or it could be neither, and it's just by design. It doesn't really matter; it's just stuff I think about when I'm sitting in a dark room for 8 hours a day.

The black level isn't identical, but it is extremely close. Not surprisingly, the smaller panel is capable of more light output and, therefore, has a higher contrast ratio. The fact that it has a little lower black level also helps. The contrast ratio for both is pretty good for flat panels, but, across the board, the numbers are worse than the previous generation of Panasonic plasmas. The 1,024-by-768 TH-42PX60U that we reviewed in November 2006 had a black level of 0.012 foot-lamberts and a light output of 27.77 ft-L for a contrast ratio of 2,314:1. The color points were roughly the same. So the tradeoff here is 1080p resolution for a poorer black level, less light output, and a lower contrast ratio. I have to say, in the case of the 42-inch, this doesn't seem like a worthwhile tradeoff. Since most people sit too far away from their TVs to see a difference between 1080p and 768p anyway, I'd say go for the higher contrast ratio of the 768p panel. For the 50-inch, it's more likely you'd see a difference in the resolution, so I'd say go for the 1080p in that case. We haven't reviewed a recent 50-inch from Panasonic, so I don't have a direct measurement comparison.

But let's put these numbers in perspective. At over 1,000:1, both panels are better than nearly all other plasmas we've reviewed (save the older Panasonics). The full-on/full-off numbers are similar to the better LCDs we've measured recently as well. This doesn't give the complete story, though. Plasmas are designed to give less light (really, they're designed to only draw so much power). So a full-white screen is dimmer than when only part of the screen is lit. You'll almost never have a full-white screen. A more accurate telling of what you'll see on the screen is by taking what the plasma can create on a 100-IRE window, which is about 18 percent of the screen. This is roughly the amount of the screen that's lit with most real-world video content. If you use these numbers, the real-world contrast ratio for the 42-inch is 3,885:1.

I'll let you in on a little secret. Every plasma we've ever measured for contrast ratio has the light output on a window listed in the measurement text. We don't use this as the main number because our official measurement is full-on/full-off for all displays. As you can see, this unfairly handicaps plasmas, so we also include the 100-IRE-window number for comparison.

But how do they look with HD? Using the 16 Blocks and Phantom of the Opera HD DVDs, I found the TH-50PZ700U to be very detailed and very punchy. The contrast ratio was such that the black bars faded into the background. With darker scenes, the black level was noticeable, proving that, as good as the black level is, this is no CRT.

Both plasmas are able to resolve a one-pixel-on/one-pixel-off pattern, but only if you change the HD Size option buried in the menu to Size 2. This confusingly named setting adjusts overscan. Size 1 has lots of it; Size 2 does not.

What about the TH-42PZ700U? It was a little brighter and therefore a little more punchy than the 50-inch. However, here's the catch. At the same viewing distance as the 50-inch (around 9 feet), the lines to test the one-pixel-on/one-pixel-off pattern were indistinguishable. If you lean in, you can make them out just fine. Seeing as most people sit even further away (around 10 feet), there is no way you'll be able to see all the detail that the TH-42PZ700U creates unless you're some kind of falcon. And if you're a falcon and can read this, then you should be able to afford a lot bigger TV, seeing as you're a bird that can read.

Both panels were very slightly noisy, but certainly better than most plasmas.

Tapping the "Wrap It Up" Box
It doesn't matter how many times I say it—no one seems to care. You don't need 1080p in a screen size below 60 inches if you're sitting 10 feet away. If you're sitting closer, then you can purchase a smaller screen. And if you want to read the math to back this up, check the January 2005 issue of HT or deep in my blog at www.hometheatermag.com. From 9 feet, you can just make out the full 1080p resolution on a 50-inch screen if you have good eyesight and squint a little.

As far as these plasmas go on their own, the 50-inch looks great, and it's priced right, so I'd recommend it. The 42-inch performs worse than its predecessors, and all you have to show for it is 1080p, which you probably won't be able to see anyway. That said, if you feel you absolutely have to have 1080p, it's still a good-looking flat panel.

Highlights
TH-42PZ700U Plasma HDTV:
• Smallest 1080p plasma, for what that's worth
• Low black level

Highlights
TH-50PZ700U Plasma HDTV:
• Strong value/performance combo
• Great detail; decent contrast ratio