Black and Blu
In a recent e-mail, an old friend and audio reviewer asked about Blu-ray players. I tried to steer him away (successfully, I hope) from what he thought was a good deal on an new, unused first generation Sony Blu-ray player. The seller had apparently almost convinced him that this was some sort of undiscovered gem, akin (though in a different application) to the early, tank-like SACD players held in high regard by some audiophiles.
The argument is often made that manufacturers pour everything they have into the first generation of players for the launch of a new format, regardless of price. This shows-off the technology, but the high cost of the players limits sales. Later players are cheapened in search of a wider market, sometimes at a sacrifice in quality. Sounds convincing, but it isn't so in this case. It's no dig on Sony to state that the first generation of stand-alone Blu-ray players from all manufacturers had issues, mostly related to functionality rather than performance. In fact, the early player that has best withstood the test of time in its functionality is Sony's own PlayStation3, which remains the champ in several important areas, including fast load times.
That was not my friend's only question. He has been contemplating the purchase of a projector for some time, and asked about the new JVC models that were shown at the recent CEDIA Expo. I responded that there were a number of exciting new projectors there and that, yes, the JVCs were certainly on our must-review list.
But he noted that he had already purchased a screen, a 110" (diagonal) Stewart Grayhawk (gain 0.9). Whoever sold him on that screen didn't point out an important fact: While any good screen will work with any good projector, if possible you should choose the projector first, then select the best screen for it.
A reviewer doesn't usually have that option, so I've chosen to use a screen I'm familiar with for all my projector reviews, and which has worked beautifully with most modern projectors: a Studiotek 130 (gain 1.3). Early in the digital projector era, however, when the black levels of the new projector designs were truly grim, I often used a similarly-sized Stewart Firehawk. But today I feel that for most projectors the benefits of the Studiotek far outweigh the slightly deeper blacks (but lower brightness in real-world applications—regardless of the rated gain) possible with the Firehawk.
I've sometimes been taken to task by readers who complain that at 78" wide (about 90" diagonal) my screen is too small. But I prefer a relatively bright, punchy picture (provided the blacks are acceptableone downside of a small screen is that it will also result in a higher black level). You'll get more immersion from a bigger screen, but the compromise in most rooms is a dimmer, less rich, and less three-dimensional image.
The SMPTE brightness standard for movie theaters is 16 foot-Lamberts with no film in the projection gate and slightly less with a clear film frame in the light path. Past experience has taught me to expect the lamp on a home projector to drop in brightness by 20-30% by the time the lamp has accumulated around 300 hours, with the progressive reduction slowing down significantly above that point. That's why I prefer to see a minimum peak brightness of 16-18 ft-L on my screen from a relatively new projector (under 100 hours on its lamp). Manufacturers claim lifetimes of 2000 hours or more for their projection lamps, but that's the time to half brightness at best. The fussy videophile is unlikely to be happy with much more than 1000 hours on the lamp, and the even fussier reviewer should plan on replacement at around 500 hours or so on a reference projector if he or she wants to make a fair review comparison with a new projector sporting a fresh lamp.
Let's say that a given projector will put 16 ft-L on the center of a 90" diagonal (78" wide), 16:9 screen with a gain of 1.3. The area of that screen is 3418 square inches. If you keep the same screen material and change to a 110" diagonal (96" wide) screen, with an area of 5177 sq. in. the light output will drop to approximately 10.6 ft-L [(3418/5177) x 16). If on top of that we change to a gray screen with a gain of 0.9, the light output will drop even further to about 7.34 ft-L [(10.6/1.3) x 0.9].
The above calculations are approximate at best because some additional but less dramatic variables will come into play, such as a change in the zoom setting of the projection lens. The subject of screen size and projector brightness is further complicated by the increasingly popular practice of anamorphic projection, which usually involves larger screen sizes. The home theater room comes into play as well; you can tolerate a dimmer image if you have dark walls that minimize the reflection of light back onto the screen. And if you have a more flexible projector, say one with a wider iris setting or higher lamp setting that provides more light than you need on the smaller screen, you can use those options to regain part of the loss. But the conclusion holds: all else being equal, a larger screen, a lower gain screen, or both, will mean a significant sacrifice in image brightness.
No rule of thumb can cover the entire projector/screen size situation completely. But if you insist on a really big screen you'll definitely need a bright projector. If your screen is smaller, you can get by with less projection horsepower, but the smaller the screen, the more important it is that the projector provides deep, rich blacks.