Home Theater/tv/projectors


QUESTION: I had two questions related to home theaters.  The first is why are some tv diagonal sizes specified in a round number (e.g. 42") and other's are specified in 1/2" smaller (e.g. 41.5").  It seems that some manufacturer's specs go by the round number and other's they cut by 1/2."  Is this really true?  Does that mean with some manufacturer's tv's, the same size can be smaller, and you are getting less tv?  1/2" seems like a big deal.

The second question I had relates to projector screens in people's home theathers.  It seems even the fanciest home theater's don't have very large screens.  What I mean by this, is when you go to an actual movie theater, the screen is very very large, and it really fills your complete field of view.  When you look at home theaters, this seems most often not the case.  You don't really see people with 200" or greater screens, or screens that fill a whole wall top to bottom and side to side.  Why is this?  Home theater projectors certainly can project stuff hundreds of times in size, but it seems people don't take full advantage of this.  Isn't the whole idea to having a home theater is to get the biggest screen/image you can so you are completely immersed?

Thanks very much.

ANSWER: TV manufacturers present and measure screen size in different ways, and have since the days of CRT-based displays. The primary difference in numbers relates to exactly where on the display face they're measuring: the usable "safe zone" (where the image is drawn) or the entire display element's face (which includes a non-viewing border where the element is anchored into the cabinet). Often the number presented in inches is a conversion (from millimeters) as well, which can produce odd numbers (like 42.75" as opposed to 43" or 42"). Generally differences of 1" or less of diagonal size are of no consequence for a television or other large-format display, as they're relatively small variations.

As far as the projector question goes, the easy and broad answer is "different strokes for different folks" - different people design their home theaters around different goals. Some more technical, and plausible, explanations for why homeowners aren't going with truly movie theater sized screens however may include:

- Physical limitation of their house/dwelling. Movie theater auditoriums are very large (comparable in size to a warehouse or gymnasium), and especially very tall - most residential dwellings don't offer 20-40ft ceilings (or if they do, they're often in rooms filled with windows) to support a massive screen.

- Limitations on what consumer projectors can do. The projector that a movie theater uses is a very large and very expensive machine (they can be the size of multiple refrigerators end-to-end, and cost more than a house to purchase, as well as very high maintenance/operating costs (they require specialized power and cooling, among other things)). Consumer projectors are generally at their maximum draw size at around 120-140" which is very reasonable for a residential installation.

- Resolution. Consumer media is, at present, available in up to 1080p from high quality sources, while movie theaters frequently use 4K (or higher) resolution prints. Projecting a lower resolution source (e.g. a DVD or Laserdisc) onto a movie-theater sized screen would result in very poor image quality, however onto a more modestly sized residential system can yield an excellent picture.

It's also worth considering that bigger isn't always better - many home theaters are designed to produce high quality picture and sound, but not necessarily to be as loud, bright, or large as possible. Think about it like buying a car: you could buy a bus or a dump truck or some other massive vehicle, but it probably wouldn't be practical for driving on residential streets, would cost significantly more to maintain and insure, and you would likely never use the extra capacity. By contrast, a nice luxury car is smaller and more reasonable to maintain and insure, will handle residential driving much better, and makes more sense in a consumer environment. Additionally, when it comes to a video-display, the size is really best matched to the viewing distance - movie theaters have huge displays because they have to accommodate hundreds of patrons, and the large screen requires people to be seated further back for total viewing (if you have a movie theater that will allow it, try walking up to a typical TV viewing distance (6-8ft) from the screen - see how much of the image you can (or can't) actually see), whereas at home you're usually only needing to seat a few people, so you don't need to accommodate stadium seating, and thus everything can scale down in size - you can use a smaller room, and that means a smaller screen (see above), but you can still achieve FOV dominance as you're moving the audience closer to the screen.

Finally, all video display technologies have trade-offs. Projectors can produce big images, but require rooms with significant light control (i.e. they don't work well with direct sunlight), and require expensive bulb replacements fairly regularly. They also require mounting and (often) wiring to be run so they can connect up to the equipment. Large-screen displays (e.g. a big LCD TV) can produce a very high quality picture as well, have much lower maintenance costs, handle better in rooms that don't have significant light control, and don't require any throw distance (a projector has to be moved further back for larger images; generally to get a 120-140" screen you need a room that's at least 10-15ft long, while you can put a 70" LCD up in your hallway if you really wanted, and watch it from 2ft away). Cost is also a factor, at least more recently, as LCD-based displays have become incredibly affordable, and it makes more sense to spend a few thousand dollars on a top-tier LCD as a one-time purchase, as opposed to a few thousand dollars for a projector, plus extra for the screen, mounting, wiring, continuous rolling costs for bulbs (which can be hundreds of dollars a piece), set-up, and so forth.

Overall all of this boils down to preference - there's nothing wrong with one setup over another, and different people will purchase whatever suits their needs, tastes, budget, etc. Technically speaking, there's nothing that says you couldn't have a larger theater in your house, but once you get past a certain size limit (as mentioned above) you're likely talking about architectural changes to the structure to facilitate that kind of install, and the bottom-line price could easily reach into the hundreds of thousands of dollars (if not more). Personally I would not accept such an expense as being "worth it" when you can get quite frankly excellent audio and video for much less by making a few compromises on size and scale.

If you have any further questions, feel free to ask.


---------- FOLLOW-UP ----------

QUESTION: Thanks for all your help.  You are so knowledgeable and detailed in your responses that you should be the "only" home theater expert on this forum.  With regards to the tv sizes then, so I guess what you are saying is that with some manufacturer's you may be getting a little less/more than what they state, even if it is 1/2-1Ē?

With projectors, you mention that they have higher maintenance costs, such as frequent bulb replacement.  This may be with LCD projectors, but what about LED projectors?  I heard that with LED, you donít have to worry about this very often, and that those bulbs last really long, as compared to LCD.  Wonít LED replace LCD altoghether eventually?

Also, when you mention it makes more sense to pick a top tier LCD tv, I thought this was not the best technology, as compared to plasma (RIP), or OLED, which is too expensive and really has not hit the market.  Everyone today really only has the LED-LCD option, which has it's own set of issues, so it seems like it wouldn't be a top tier option over projectors (e.g. picture quality, Motion Interpolation-"soap opera effect").  Seems like projector is closer to plasma/OLED.

When you mention size/viewing distance with projectors, do you think everyone should look at what THX recommends as what the viewing angle should be for home/cinema?  I think they recommend something like the screen image should fill at least 40% of your field of vision in order to have the most immersive experience.  I think they calculate that off the last row of seats in a movie theater having that viewing angle.  Is this really a magical formula?

With regards to both tvís and projectors, does brand name really matter?  You hear so much conflicting views of this nowadays.  I know especially with tvís nowadays, you see so many ďoff-brandsĒ for such good prices.  Some say they donít last as long or they're not as good.  I even saw some forums that said even name brands get their same parts from factories that produce parts for off-brands so it is all the same any way you look at it.

From the top:

1. Yes, technically. Generally that slight difference between panels will go unnoticed in practice, and generally you will see consistency between manufacturers (e.g. two different brands selling a 50" TV should be using the same size panel).

2. Not just LCD projectors, but DLP, SXRD, and LCOS as well. Technically CRT and LED-illuminated (which can include any of the prior-mentioned display topologies) don't require frequent bulb replacement (LED illuminaries can fail, but their life-cycles are usually many tens of thousands, if not hundreds of thousands, of hours - CRT guns for a projector aren't quite as robust, but they will outlast the high intensity bulbs that have become common. However both of those projector types will be less bright, and require more aggressive light control for a suitably high contrast image. In the future it is likely that LED luminaries will replace other light sources, such as CFLs (as in older LCD monitors), or high intensity arc bulbs (as in projectors). Keep in mind that the LED is only a light source, and that you're still creating the image with some other technology (e.g. DLP, SXRD, etc) which will have pros and cons of its own. There have also been attempts at creating "laser projectors" - both systems that use a trio of RGB lasers as light sources for a DLP device, and systems that actually use a high speed laser scanner to draw the image out in real time. In both cases these have proved impractical due to cost (laser-illuminated projectors, when available, were well into the five figure price range; the "laser scanner" model is into the eight figure range and requires an equipment room for power distribution, cooling, etc (some planetariums use this kind of projector though)). In the future, lasers may become cheap enough to be a viable competitor to LED-based illumination, but that's certainly not the case today (as far as "what advantages do they have?" - the laser-illuminated systems have very good color accuracy, the laser-scanned systems have exceptionally sharp images and very high redraw rates as well).

3. All display technologies have their pros and cons. I wouldn't regard LCD as universally inferior or superior to PDP, OLED, SED, CRT, etc. In general, I think it is fair to say that LCD-based displays represent a better compromise for consumer usage than other display technologies - they aren't susceptible to image retention, they're affordable, they can be very power efficient, they can be quite fast, and they offer a very uniform picture. "Future technologies" like OLED and SED offer similar advantages, but currently are not economically practical in comparison to an LCD, and in practice may not offer subjectively superior image quality (there is absolutely a point of diminishing returns). As far as a projector "being closer" to one of those technologies, I would not agree. Projection systems require care and attention to their installation and the room's light control in order to achieve a good contrast ratio, and not all projectors offer equal quality optics, light sources, or display elements - with very cheap systems you can have all sorts of visual anomalies that you wouldn't experience with an LCD or PDP display, for example. Again, it's all pros and cons - depending on your application requirements there may be a reason to preference one system over another. For "typical" home systems, a large LCD display is very likely the most economical and user-friendly solution, and should have the lowest long-term upkeep considerations, especially if it is LED backlit. For higher-end systems, it can still be a good choice depending on the size of the room, budget, etc, or a more robust projector may be a reasonable consideration if budget and architecture allow.

4. I would not consider THX's suggestions "a magic number" but they're certainly a useful guideline. You don't want the screen to be over-large relative to your FOV, nor do you want it to be at an uncomfortable viewing angle, which the THX guidelines will roughly lead you to. "Immersion" is a very subjective qualifier - its hard to quantify that or build a spec-out from it.

5. Generally I would preference a "brand name." While it is true that there's a lot of commonality between equipment, for example there's only a few manufacturers in the world that actually make large LCD panels, and there's only a few manufacturers in the world that actually make certain control logic, power regulation modules, etc for those devices (and therefore you're not going to see miles of difference between display designs), that isn't the whole story of the device. You also have to consider the software/firmware that sits on top of that hardware and makes it work, and generally this is where the "brand name" devices separate themselves from the no-name knock-offs. Support and warranty is also something to keep in mind - a no-name company may be gone without a trace in a month.

5a. You mentioned Motion Interpolation (MI) above - this would be an example where a "brand name" can delineate itself from no-name competitors. Generally more advanced features like that (and the DSPs that run them) are only found on nicer and more elaborate designs. Whether or not these post-processing features are worthwhile to you is an entirely subjective matter, however.

If you have any further questions, feel free to ask.


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