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Friday, December 1, 2023

Rear projection vs. LCD vs. plasma

Rear-projection TVs used to be the only way to get the “big-screen” experience at home. With the advent, and diminishing price of, large flat-screen LCDs and plasmas, the RPTV has become something of an endangered species. In fact, only one company, Mitsubishi, still makes RPTVs.

Many people still enjoy their RPTV, and I’ve received several letters recently asking if it was time for them to upgrade.

Are RPTVs a viable alternative to flat panels? When should you upgrade your old RPTV? Let’s break it down.

Like my “LED LCD vs. plasma vs. LCD article,” I’m going to do this as objectively as possible, keeping my subjective thoughts at the end.

Also like that article, I’m going to start with a big disclaimer (cut and pasted, actually): Any article of this type is, by necessity, going to contain a lot of generalizations. In most of the categories below, there are likely one or two exceptions to each rule. It’s great to find an outlier, but that’s just what it is, an outlier. The “average” product featuring these technologies is going to perform as listed.

With this article, though, it’s a bit easier, as the current RPTV category has only one brand, and all the models are based around DLP technology.

So what do I mean by RPTV? Rear-projection televisions in the HD era came in many flavors. While flat-panel TVs struggled with price, LCD, LCOS, and DLP RPTVs dominated the big (50-inch+) market. There were even some CRT RPTV stragglers in the early ’00s, though those soon disappeared (thankfully, as they were ridiculously heavy).

At the bottom of a RPTV, there’s a light engine (either DLP, LCD, LCOS, or CRT). This fires upward into a big mirror, which reflects the image out toward a semitransparent screen. The light that makes it through this screen is what you see as an image.

Today, only Mitsubishi continues to make RPTVs. All use DLP to create an image. Most models use UHP lamps (like front projectors), but some high-end models use lasers. The lasers last the life of the TV, the lamps do not (though you should be able to get a few years out of them before they need replacing).

I’m going to keep with the same format as the LCD vs. plasma article, but just talk about the specifics with RPTVs.

Light output (brightness)
Winner: LED LCD
Loser: Plasma
Runner-Up: CCFL LCD and RPTV

LED LCDs are the brightest displays you can buy. You’re pretty much never going to need that much light output. Newer RPTVs can be pretty bright, with the laser models putting out near-LED LCD performance in this regard.

There’s a catch, though. An RPTV screen is somewhat two-directional. As in, because it lets light out (the image), it also lets some light in. In a well-lit environment (lots of windows, say), all of that ambient light is going to enter the screen, bounce around inside the RPTV’s cabinet, and eventually come back out again. Some of the light will reflect off the front screen surface, too, just like any TV. The result? The image is going to wash out. So if you have a lot of windows and like watching TV during the day, an LCD (especially a matte screen one) is still your best bet.

Black level
Winner: Plasma
Loser: CCFL LCD and RPTV (some)
Runner-up: LED LCD and RPTV (others)

Thanks to dynamic auto irises, and dimming light sources, RPTVs can have a low black level (see contrast ratio section). However, because of all the light bouncing around inside the cabinet, it’s rare to get an absolute black. Many RPTVs had a terrible black level, going instead for maximum light output.

Contrast ratio
Winner: Plasma
Loser: CCFL LCD and RPTV (some)
Runner-up: LED LCD and RPTV (others)

When I talk about contrast ratio, it’s important to understand where I’m coming from. Manufacturer specs are worthless. Dynamic contrast ratio, what all manufacturers specify, is what’s possible between two different scenes. Native contrast ratio, what’s possible during a specific shot (as in the darkest and brightest part of the screen at any one moment) is vastly more important. It’s what gives and image depth and realism. LCDs have gotten a lot better in this regard, local-dimming LCD especially, but the better plasmas are still out perform them. Check out my article “Contrast ratio (or how every TV manufacturer lies to you)” for more info.

All RPTVs have the problem of some light reflecting of the back off the screen, bouncing off the mirror, and washing out a different part of the image. So even the older RPTVs based around LCOS (which has the best contrast ratio potential of any of the modern technologies), don’t have as good a contrast ratio as front projectors based on the same technology.

The dynamic contrast ratio, especially those augmented by an automatic iris, or a dimmable light source (the laser models), can be quite impressive with RPTVs. Because of the internal reflections, though, the native contrast ratio isn’t great.

Mitsubishi’s RPTVs solely use DLP. While I generally like the look of DLP-created images (they have many strengths), native contrast ratio isn’t as good as some other technologies.

The short version? Most current plasmas have a vastly better contrast ratio than nearly all RPTVs.

Viewing angle
Winner: Plasma
Runner-up: IPS LCD and RPTV

The biggest issue with RPTVs is the screen itself. In order to get the most light output, manufacturers use what’s called a lenticular screen. It’s quite like the lens system in a lighthouse. This screen takes the light that would have otherwise gone toward the ceiling, floor, or sidewalls, and focuses it toward the viewer. While this adds brightness, in extreme cases it causes hot spotting, or the center of the screen being noticeably brighter than the edges. In addition, it means that if you sit off axis (not dead center), brightness is affected. Not nearly as badly as some LCDs, but in most cases, not great. If you have a wide seating area, plasma is the way to go.

One other side-effect of most RPTV screens is a speckle/sparkle effect, almost like tiny pieces of glitter on the screen. I’ve always found it annoying, but many people don’t mind it at all.

Energy consumption
Winner: LED LCD and RPTV (some)
Loser: Plasma
Runner-up: CCFL LCD and RPTV (others)

According to the Energy Guide labels for Mitsubishi laser and UHP models, energy efficiency is quite good. For example, this 75-inch LaserVue model is rated at only $20 a year, far below the range of other 69.5-inch and larger models (label found on Amazon). This 92-inch is $44, at the bottom of the range. The largest regularly available plasmas, around 65 inches, are roughly equivalent in power consumption as this much larger RPTV, according to the FTC. Comparable size plasmas (i.e. Panasonic’s 103-inch) aren’t rated by the FTC, but it’s safe to assume they’re drawing a lot more than $44 a year in power.

Winner: CCFL LCD and RPTV
Loser: LED LCD
Runner-up: Plasma

When it comes to dollar-per-screen-inch, RPTVs are still fantastic. This is where they excel. While Mitsubishi’s MSRP prices are, shall we say, optimistic, the retail prices are quite impressive. Nowhere else can you get a 73-inch TV for $1,150, an 82-inch for $1,600, a 92-inch for $2,600, and so on.

The LaserVue models, however, tend to bump up very close to flat-panel TVs prices of roughly similar sizes.

Winner: LCD, LED LCD, Plasma
Loser: RPTV

Historically, RPTVs have had a pretty terrible service record. UHP lamps generate a lot of heat, so there are multiple fans to get that heat out. One fan failure can lead to total TV safety mode shutdown. Then there’s the UHP lamps themselves, literally a wear part, which need replacing every few years. Mitsubishi has been doing RPTVs longer than any company at this point, so I would assume it has the bugs worked out, but the fact is there is more that can go wrong in a RPTV than a flat-panel.

Related stories

Winner: RPTV
Loser: LCD, LED LCD, Plasma

DLP can’t burn in. Stuck mirrors can happen (though not terribly likely, in my experience), but I’d file that under lifespan, not burn in. All the other technologies can have image persistence and/or burn in. Check out “Is plasma burn-in a problem?,” which also covers LCD image persistence.

Winner: Plasma

As we discussed, the lenticular screen can cause hot spotting. Personally, I find mild hot spotting less objectionable than random poor uniformity. Historically, depending on the RPTV cabinet, there can be internal reflections that cause random bright spots. This is a binary category in my mind; you either have perfect uniformity or you don’t. I’ve seen some LCDs with far worse uniformity than the RPTVs I’ve reviewed, but the latter still aren’t as good as the average plasma in this regard.

Check out Is LCD and LED LCD HDTV uniformity a problem? for more info.

Bottom line

The questions I’ve recently received from readers is whether modern flat-panels offered enough of an improvement over their older RPTVs for me to recommend an upgrade. If you’ll allow me to enter the subjective section of this article, I’d say: depends. There were so many RPTVs over the past decade that were quite good (and many, many, many terrible ones), I can’t say definitively yes or no. Generally, if you have an older (6 years+) LCD- or DLP-based RPTV, modern LCDs and plasmas will probably look a lot better. Most of the LCOS models (from Sony, mostly) looked pretty good for the few years they existed. For them, and the last few generations of LCD and DLP RPTVs, the answer is less clear-cut. The cost of new lamps is probably a deciding factor at that point as much as picture quality.

One caveat: HDMI. If your TV doesn’t have HDMI, you’re going to be left behind. The analog sunset has set, and you can’t buy new Blu-ray players with component outputs. Most new gear (like the Apple TV, for example) only have HDMI.

On the other side, should you consider a new RPTV? Maybe. There are few reviews of the newer RPTV models. I’ve only seen them at trade shows. However, I review tons of DLP displays (front projectors), and the RPTV version of this technology isn’t much different. So I’m familiar with the overall picture quality, minus the normal RPTV drawbacks. In other words, it’s good, though LCOS (in front projectors) and plasma likely perform better in certain categories, most notably contrast ratio.

The biggest issue for most, of course, is the bulk. Though far thinner than CRT RPTVs of yore, modern RPTVs still have considerable depth compared to flat-panels. For some people, this is a deal breaker. I would offer one counter to this potentially off-putting girth: are you really going to notice? Most people never mount their TVs, leaving them on stands 12 to 18 inches away from the wall. So who cares if the TV is that depth? Just offering an argument, not trying to persuade you either way. Flat-panel TVs are still cool, and that coolness isn’t directly quantifiable.

The biggest benefit by far of an RPTV is screen size. As we’ve mentioned, you just can’t get flat panels in the sizes of modern RPTVs for a similar price. I’m a vocal proponent of front projection, but concede their inability to deal with ambient light. While RPTVs aren’t as good for ambient light rejection as LCDs or even plasmas, they’re way better than front projectors.

So I guess that’s the takeaway: if you want a massive screen, don’t want to spend the money on a huge flat panel, don’t want/can’t have a front projector, and don’t mind the depth, check out an RPTV.

Any old or new RPTV fans out there? What made you upgrade to or from a rear-pro?

Got a question for Geoff? Click “Geoffrey Morrison” below then click the E-mail link in the upper right to e-mail, wait for it…Geoffrey Morrison! If it’s witty, amusing, and/or a good question, you may just see it in a post just like this one. No, I won’t tell you what TV to buy. Yes, I’ll probably truncate and/or clean up your e-mail. You can also send me a message on Twitter: @TechWriterGeoff.

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