The needs of museums, educational institutions and conferencing venues differ from those of the cineplex, and digital cinema as it is right now does not always meet them. There are benefits: print cost goes away, the last run of the image is just as good as the first, a multiplex can quickly reschedule theaters based on today’s ticket sales. But for theaters with screens wider than 20 feet, you pay a price in image quality. Today’s DCI compliant systems (Digital Cinema Initiative, keeper of the industry standard) supply a moving picture only 1/4 to 1/10 of the picture information you could see in the typical 35mm movie house – just slightly better than really good broadcast TV.
Here’s an analogy: Think back about 15 years, to the dot matrix printer. You may have had one connected to your computer. If you shelled out big bucks you could even get a color dot matrix printer. Remember what a printed page of words looked like? At around 24 dots per inch, it was readable, but nothing like the quality of text that you are reading now.
DCI compliant projectors get you 2,048 dots or pixels across your projected image, whether your screen is 20-feet or 100-feet wide. The equivalent resolution in film, depending on the physical size of the film stock (from 16mm all the way up to 70mm 15-perf) is in the range of 8,000 to 20,000 dots, or pixels, of information across the width of the screen. Going back to the printer analogy, would you buy the argument that your current high-res color laser printer should be replaced with an old dot matrix?
DCI has done a great job in setting the bar as high as possible for right now. And right now, for best results, the image size in a digital cinema auditorium should be limited to about 20-feet wide. And the best seats in the house are going to be at least 20 feet away – any closer and a critical viewer can see the dots that make up the image. This is based on my observations of numerous film and digital projection systems over the last 30 years, from projectionist to system engineer, and including my experience in the certification of large format theaters.
Why can’t DCI set the bar higher right now? It’s the chip. The industry’s one primary chipmaker, Texas Instruments, currently only has what is called a 2K chip. This chip has 2,048 dots or pixels across it. The image on the chip is updated 15 to 60 times per second as required by the presentation – the equivalent of a 15 fps to 60 fps film frame rate. (The higher frame rates are used in some forms of 3D with glasses that shutter between left and right eye.)
Of course, the industry is working to improve image quality. Sony has a 4K system. JVC has a process that claims even higher resolution – shown last year at the National Association of Broadcasters (NAB). Some systems blend images from multiple projectors. (At least one firm claims it can blend 100 projectors together – think about the commission on that sale! Better yet, buy stock in the lamp manufacturer before you sign the deal.) Some fresh advances may be unveiled at NAB’s Digital Cinema Summit in Las Vegas this April 12-13.
Getting back to today’s DCI compliant projector – for the sake of easy math, let’s say it has 2,000 side-to-side pixels. Project it onto an 80-foot wide giant screen. That gives 25 pixels per foot, or two dots of content for every inch of image. Put the same image on a 40-foot wide multiplex screen: 50 dots per foot or 4.2 dots per inch – better, but I still would not want to be sitting in the front row. In film terms, you would have a very grainy image. So if you want to provide an immersive experience showing the breathtaking vistas of Africa or outer space, or a visually detailed nature, history or science documentary, for now you should stick with film.
On the other hand, if you are installing or updating a small, 40- to 200-seat theater, then let’s look at digital. On a screen 16-feet wide by 9-feet high, you will have about 120 pixels per foot, depending on the projection system you select. This is much better than the “grainy” 25 pixels per foot in the giant-screen example above. But note that it doesn’t compete with the quality of good home theater. It is a far cry from the 480 pixels per foot that give home viewers a picture window to the world on their digital flat panels.
The advantage of a small, digital theater system with DCI compliant projectors is that it makes a great, versatile screening room with options far beyond what you get with a film projector. Content changeovers are very fast. A good laptop can drive the system. Your theater becomes a space you could rent out for corporate meetings or educational sessions, or the local ad agency. If the projector has a DVI input port, and the computer has the same output (anything sold in the last 18 months has it), the system is even more versatile. Digital cinema greatly simplifies 3D presentation and right now 3D is hot. There are systems on the market that will allow you to change over from 3D to 2D in the time it takes to re-cue your video hard drive.
If you have a small theater that has multi-use needs or if you can produce your own show in full high-def video, then a digital projection system is what to look for. If, however, you want or need high-quality visual resolution and color depth, these are still much more attainable in the realm of film.