Projection TVs - Help needed!

[Brain Sturgeon]

Originally Posted by Siniroth

I need some help regarding projection TVs.

Okay, first off let me say I just recently decided that I was going to get the new 50" Panny V10 Neo Plasma (which comes out in May). I was all excited about it and everything, but for all that time it took me to settle on that one model, I started reading through a couple of threads in this forum about PJ TVs, and I'm already feeling the dreaded "buyer's remorse", even though I still have several months yet to even purchase the TV!

I had looked at a few galleries of people's PJ set-ups in the past, always jealous because I'd never be able to afford something so big. But then I started seeing some pricing, and I realized, that pricing isn't too much more than the $2k or so that I was/am going to shell out for a high-end Plasma! Considering I don't know anything about PJ TVs, I thought it couldn't be possible to be able to get those crazy 100" screens for a decent price. How is this possible? Lol.

Anyway, I'm starting to really second guess my decision to go Plasma, and am instead thinking about a PJ. Few things I want to ask about though (please excuse my noobish questions :P):

-What is the difference between front and rear projectors?
-What is DLP?
-Why do I see 'LCD' on some of projectors I've looked at. Isn't LCD just the Flat-Panel TVs (similar to Plasma)?
-What is this 'CIH' abbreviation I keep seeing?

Now, I'm moving into an apartment later this year, so no, I do not have my own house. An apartment is what I'm going to be moving into, so Idk if this will be big enough for a big 100" (or so) screen? I'm hoping to find an apartment with a basement, because that would be the only logical place I could think to use as a 'home theater room' with a PJ.

If I decide to go this route (getting a PJ), then I'd just buy a screen. I'd feel much more confident in getting a pre-made screen rather than me having to paint myself one.

Tbh though, either way I'm most likely going to get the 50" V10 Panny Plasma I mentioned earlier no matter what. So I guess I'll have to get both over the course of the next year. The Plasma would probably be in my living room or bedroom, with my DirecTV HD-DVR and my game consoles hooked up to it, with the PJ being mainly used for Blu-ray movies.

That is, if I decide to get a projector. Does a solid projector look as good as a higher-end Plasma (like the new Panny I'm going to buy)? Because I'll want to watch Blu-ray on whatever looks better.

Any help you have, whether on these specific questions or anything else you think I should know about PJs, I would really appreciate.

A front projector is a two piece set up where a projector projects an image onto a separate screen.

A rear projector (RPTV) is typically a one piece TV where there is an internal projector in an enclosed box that fires an image onto a mirror which then reflects the image onto a panel (Fresnel) which then focuses the light into a cone shaped path to improve brightness. There is another variant of a two piece system where a projector fires onto a separate transmissive screen material from behind that also might be called rear projection.

DLP (Digital Light Processing) is a technology owned by Texas Instruments which is a small chip that has many nano-mirrors that reflect light. It is also known as a DMD (digital micromirror device). The most recent chipsets use 1080x1920 arrays of mirrors such that each mirror represents one pixel in the eventual picture. A light source sends light to the chip, and these mirrors rapidly toggle between on and off to produce grayscale. Projectors/TV's using DLP can be single chip or multi-chip (typically three). In a single chip unit, a color wheel is used to send different colored light to the chip which then uses the mirrors in on/off states to modulate the colors. In a multi-chip unit, a different primary color (red, green, blue) is handled by each chip.

Projectors can also use LCD technology in which light is passed through a transmissive LCD panel. These tend to make up the "lower" end of the projector market, although recent models by Epson and Panasonic are excellent.

CIH stands for "Constant Image Height". It is a way to watch the common aspect ratios for movies (1.85 or 2.40) without black bars above and below the picture. The screen height is held constant in this kind of a setup, whereas the width is changed for the different aspect ratios.

2.40:1


1.85:1



There are two ways of doing this currently: the "zoom method" and using an anamorphic lens with a image scalar (frequently built into projectors nowadays).

The "zoom" technique is simply using the zoom lens on any projector to fill a 2.40:1 screen, with the black bars falling above and below the screen. You can do this with any projector as long as you are within the appropriate zoom range for your given throw length.

The "lens" technique places an anamorphic lens (typically a 1.33 horizontal expansion lens) in front of your projector's lens. Your projector, or your outboard video scalar, would then need to vertically stretch the projected image 1.33x so that the black bars are excluded from your image panel. As the vertically stretched image passes through the anamorphic lens, your image is reconstituted into the correct aspect ratio onto your scope screen.

There are good and bad things about both:

"zoom" technique
pros: cheaper, easier projector setup, no pincushion introduced into the image.
cons: Reduced horizontal resolution, need to rezoom when switching between 1.85:1 and 2.35:1 material

"lens" technique
pros: Uses the entire imaging panel (full horizontal resolution) to create the image, brighter image (up to ~20% brighter than using the zoom technique), quicker and more elegant switching between aspect ratios (can be done by moving lens in/out using manual/automated sleds and turning the vertical stretch on/off, or by leaving the lens permanently in place and adjusting the aspect ratio electronically using your projector or an outboard scalar, or by using one of Prismasonic's lenses that leaves the lens in place and switches between anamorphic and non-anamorphic "pass through" modes)
cons: introduction of pincushion distortion into the image, reduction of MTF and subsequently ANSI contrast by introduction of another lens into the light path, more expensive, more complicated projector set-up.

Most reasonably sized rooms (10x10 or more) can be set up with a front projection system, although part of this depends on your projector's specs in terms of what throw ratios it can handle (directly associated with the zoom capabilities of the lens). A throw ratio is the ratio of the distance of the projector lens to the width of your 16:9 screen.

General rule of thumb with screens: go with the largest size that you feel comfortable with.

Light control is probably the most important aspect of having a front projection system. If you do not have decent light control and want to do some or a lot of the viewing during the day, then go with a flat panel TV. Otherwise, if you have good light control, the size impact and cost/size ratio for front projection systems is really unbeatable. The image quality of a good FP system can be excellent, rivaling even the best of plasma TV's. Picture quality wise, it is difficult to beat a flagship Kuro; but throw size into the mix, and a good FP system will win hands down for overall image impact.

HTH!