Digital Light Processing, known more popularly as
DLP, is an
image projection technology which will most likely replace
film projection in
cinemas. The technology has existed since 1996, but adoption by
exhibitors (i.e. theater chains) has been slowed primarily by debates about how theater conversion costs will be divided between
studios,
distributors and exhibitors. DLP can be used in other ways (hence the P standing for "
processing" and not "projection"), but I'll leave those implementations to other writers.
THE BENEFITS
Why replace film as a projection medium?
- Lower Distribution Costs: It is extremely expensive to have many thousands of release prints made for each movie. Once those prints are made, they must be shipped. Prints are several thousand feet of film and are veryheavy. Weight = high shipping costs. Also, prints can be lost and/or stolen (as were several prints of Star Wars: Episode I: The Phantom Menace). The DLP system allows the content to be transmitted by secure digital satellite link to exhibitors. No prints, no shipping.
- Content Variety: DLP projection systems don't have to only show movies. An exhibitor could, if they so chose, use their DLP-equipped theater as a replacement for Pay-per-View. Boxing matches on huge screens, concerts with 5.1 surround sound, etc. The variable here is whether or not audiences would be keen on going to movie theaters for this type of thing... but the public's desires are a problem for marketing.
- Better Image Quality: DLP does not have a resolution equal to film, but many things about the projection process degrade a film image enough that a DLP projection can and does look better.
- Once it is installed and calibrated, a DLP projector will not go out of focus. A film projector is continually being refocused every time a new print is loaded, and I'm sure you've been to films where the projectionist hasn't been able to focus properly.
- Since there is no film, the film cannot jump and jitter in the projector gate (which is also absent) causing an unstable image. There is no film to get scratched or dirty. Or break.
- There are no changeovers between reels with DLP, because there are no reels. Even though most prints are spliced together into platters these days, and therefore reels aren't actually changed, there is still a jump in both picture and audio (not to mention a visible change-over mark) at the interface of each reel. Also, when editing, editors must allow scenes at the heads and tails of reels to "hang" a bit, to make sure no important action is accidentally spliced out when reels are switched or joined. DLP allows you to see the entirety of those "hanging" frames (which may or may not be a good thing), but if it is adopted entirely it may eliminate the need to edit for reel changes at all.
THE TECHNOLOGY
Here's the beef. At the heart of a DLP projection system is what Texas Instruments (the place where Dr. Larry Hornbeck invented it) calls a Digital Micromirror Device or DMD. Yes, folks... it's all done with mirrors. The DMD is a collection of 1.3 million hinge-mounted micromirrors. How micro? Each mirror is less than one fifth the width of a human hair, and the distance between mirrors is less than one micron. One mirror per pixel gives you an image of 1.3 million pixels, maximum. This is a lower resolution than a film frame, but that's acceptable for the reasons listed above. Each mirror's hinge is controlled by a micro servo (yes, it's all micro) which points the mirror either into the light source being projected onto it, or away from the light source.
Off or on. Light is either being reflected, or it isn't. Part of the DLP content is code which tells the mirrors when to switch, and there can be several thousand switchings per mirror per second. The fewer "on" switchings per second, the dimmer the pixel on screen. As such, a DMD is capable of producing 1,024 (recognize that number?) shades of gray per pixel, which is a very acceptable contrast range.
But what if you're not being all arty, and your movie is in color? Hey, DLP can handle that. Is 35 trillion colors a wide enough palette for you? The color technology in DLP Cinema systems hearkens back to the days of Technicolor and the three strip process; a DLP Cinema projector has three DMD chips. White light from the system's internal 15,000 lumen projector is passed through a prism which refracts it into red, green or blue light. Each color of light is projected onto its own DMD chip. To display any color other than red, green or blue, the mirror on each DMD which corresponds to the pixel to be colored (remember... all three DMDs are having the same image projected onto them) will alternate projecting one of the three colors for the proper amount of time to let the colors blend in your persistence of vision. For example, to create a yellow pixel, two corresponding micromirrors will alternate flashing; one for the blue and one for the green. The rate at which they flicker controls the intensity (i.e. the saturation) of the color. So, yes, DLP has a refresh rate just like your monitor... however, it's per pixel instead of per frame and is at a rate of thousandths of a second.
All of this flashing and reflecting light is, of course, directed into a lens which is pointed at and focused on the screen. The image from each DMD has been combined into a single, full color picture.
THE (CURRENT) VERDICT
DLP should be adopted across the board as the projection medium of choice. Essentially, it makes content captured on film look as good as it possibly can when projected. I have seen several DLP screenings, and the difference is immediately apparent when the first green band appears at the head of the first trailer. The image is rock solid, the letters aren't jumping around, there is no dust and are no scratches. Once the film begins, I would not know I wasn't watching an utterly perfect film print except for some aliasing on lettering. If you are sitting in the first two rows you might find the overall pixillation noticeable, but it's never bothered me. DLP will also require that capture media stay at an extremely high quality, as the nastiness of most video formats will be all the more apparent when projected in DLP. George Lucas found a way around this with his all-digital Attack of the Clones by significantly up-resing his video source material and adding simulated film grain to it. Otherwise, even shooting 24P High Definition video won't really cut it... shoot film!
DLP is really the first major and important advance in film image exhibition since the advent of anamorphic lenses, and I'm going to be a huge cheerleader for it.
Technical hoo-ha derived from http://www.dlp.com, Texas Instruments' DLP site.