Front Projection 101

Videophiles and movie fans are like cousins who espouse different religions—they share a family resemblance but have fundamentally different worldviews. For videophiles, the meaning of life can be found in a well-produced college baseball game that runs repeatedly on HDNet—dazzling in its own right, despite its lack of drama. For movie fans, nothing beats the immersive experience of a darkened theater, where for two or three hours they can go on a thrilling journey without leaving their seats.

Movie fans admit that films can be enjoyable on smaller screens but grumble that even the largest plasma monitors leave a bit to be desired. Films are meant to be seen big, and the only way to get that immersive bigness is via a projector. For true-believer movie fans, a projector isn’t a luxury; it’s a necessity.

Once the domain of a few manufacturers—Barco, NEC, Runco, Seleco, Sony, Vidikron—video projectors during the first two decades of the hometheater era were massive, delicate, cathode-ray-tube (CRT) monstrosities that required piano movers to install and factory-trained technicians to tune-up and maintain.

The best CRTs were (are) capable of truly film-like performance. Many hometheater enthusiasts still feel that CRTs are the only true path to cinematic Nirvana, and a thriving underground of CRT gurus serves them, now that manufacturers have moved on to other technologies.

Price Erosion and the Performance Explosion

For the rest of us, the market has exploded with an incredible number of lightweight, high-performance projectors that are almost maintenance-free and easy to set up, delivering big bright images at prices undreamed of a few years ago.

Advancements in basic technology and large-scale manufacturing are bringing the cinematic experience to an ever-increasing number of homes at ever-decreasing costs. Decent performance can be had beginning at around $1000. In Issue 62, I reviewed the Optoma H31, a little $1300 DLP projector that, apart from a slight color inaccuracy, performed amazingly well for its price. In the same issue, Video Editor Shane Buettner reviewed the Faroudja DILA 1080pHD, a three-chip statement-product with a price somewhere north of $40k.

Between these extremes products range from fair to excellent, with the best values in the $3500–$5000 range. Sony’s $3500 Cineza VPLHS51 is a fine example. A high-definition three-chip LCD projector, the VPL-HS51 delivers performance comparable to DLP projectors costing $10k–$12k (see the full review in Issue 61).

Some Background

Movies look like continuous motion to us because of an ocular phenomenon called persistence of vision. When you look at a light bulb, then close your eyes, you’ll see an after-image of the bulb that slowly fades to darkness. A movie is actually a series of such light-bulb-like still shots (“frames”) displayed sequentially. With a bright light shining through the film, the projector’s shutter opens for one frame, then closes and opens for the next. A lens focuses the image on the screen. Synchronization between projector and film (and persistence of vision) makes the individual frames blend into realistic action.

Entertainment technology has always been a compromise between the limits of possibility and the realities of economics. In the early days of the film industry, researchers conducted tests to determine an optimum frame rate—one that for most viewers, most of the time, would appear as flicker-free uninterrupted motion. That rate was standardized at 24 frames per second (fps). Some people outside the bell curve see flicker at that rate—as they do with computer monitors set to a 60Hz refresh rate—but most don’t. There have been experiments demonstrating that perceived realism increases directly with increased frame rates— 70fps is reputedly amazing—but the costs of making and screening such high-speed films are staggering. For compatibility, the video cameras sometimes used in the film industry also operate at 24fps (in video parlance, 24p).

The advent of television improved on the film industry’s frame rate, from 24fps to 30fps. In the early days of television, movies for broadcast were shown on a small screen, where they were captured by a video camera. This is how inexpensive film-to-video transfers are still done, with film projector and video camera side-by-side, focused on the same plane. Differing frame rates cause flicker in the copy, common in old home movies transferred to video. One way around this was to boost the speed of the film projector to 30fps, 25% faster than normal, yielding low flicker but accelerated motion. Today we have a frame-rate-equalizing technique called “3-2 pulldown” to allow seamless video display of filmbased originals. Three-two pulldown is built into most modern video playback gear—but not all and, most baffling, not all projectors. It’s essential for movie lovers. Higher frame rates and horizontal scan rates in high-definition video equipment necessitate “scalers,” circuits that convert one video standard to another. Once expensive stand-alone processors, scalers are now built into many products.