For a movie buff, what could be better than watching a movie exactly the way the director intended it to be seen? And for most directors, having the audience see their movies with the same high quality picture and sound seen in studio screening rooms is a cherished dream. Today, digital cinema technology is beginning to make their dream come true. This represents a huge leap forward from the photochemical world where image quality is degraded through the release printing process, distribution and normal play in theatres.
We all recognize that 35mm film has many strong qualities, chief among them its large dynamic range, wide color gamut and ability to resolve fine detail. But let's also recognize its quality limitations. The photochemical color timing process is imperfect. Despite advanced film emulsion technologies and some new tools in the lab, the process remains non-realtime and extremely difficult to control. Results vary from lab to lab and day to day. In addition, the release printing process has been pushed to its limits by the demand for huge "day and date" releases around the world. Prints being delivered to theatres are made from a 3rd generation master and printed on high speed contact printers that do not have the ability to maintain constant registration or color. Because prints are made in 2000-foot rolls, results can vary at reel changes, often changing dramatically in density or color. Film projectors contribute to the degradation of performance with their often-violent pull-down mechanisms and unsteady gates. Finally, print degradation is a given. The print gathers dirt and scratches from its first screening and suffers color fading from constant exposure of the emulsion to heat and light emanating from the xenon lamp. Those familiar with high quality answer prints, studio screening rooms and top-quality film projection systems often overlook this litany of shortcomings, but even in major cities and top quality theatres, ticket-buying audiences are subjected to film presentations that compromise the director's vision on a regular basis.
How can digital mastering and projection technologies deliver on their promise to bring the director's print to every theatre?
Digital Mastering
Many of the movies that have been digitally released were digitally originated: captured with 24P cameras, or created in CGI. For film-originated titles, mastering generally follows one of two routes: HD telecine, most often from a 35mm interpositive, or the digital intermediate process …quot; using the camera negative as a source. However, once the source content has been digitized the process for making a distribution master is similar. Color timing is done in a mastering theatre with a large screen and a digital cinema projector. In current practice, DLP cinema projectors are used in mastering theatres. The projectors have the same image characteristics as those in commercial theatres. The director or cinematographer see the changes they and the colorist make in real time. The sophisticated color timing hardware and software in combination with the large screen projected image enables the director to create and see the desired look in the digital timing sessions. Flexibility and control in digital mastering provide great opportunity to create seamless effects, transitions and a consistent look from start to finish. Once the look is approved and locked, the movie is laid to hard drives or tape, creating the director's digital answer print.
Visually Lossless Distribution
The print must be encoded, encrypted and packaged next. Although digital cinema formats are not yet standardized, several acceptable options exist. All formats being used in mainstream theatres today for digital cinema distribution have met the "visually lossless" standard. It's true that some experts can see the difference between the digital answer print and the encoded digital print, but normally the difference is visible only in still frame and at distances under a single screen height. The method of distribution varies: Satellite, data tape and optical disks are all used for delivery to theatre. Unlike with current 35mm film distribution, no degradation of the picture takes place as a result of the digital distribution format, leaving the movie presentation visually identical to that the director approved.
Calibrated Exhibition
At the theatre, the distribution media is loaded into a server and at playtime, decrypted and decoded. The digital projector and server are extremely stable and the source does not degrade over time. Current digital cinema exhibition uses DLP Cinema projectors, designed to meet a tight set of image quality characteristics that is consistent from manufacturer to manufacturer and across the spectrum of DLP Cinema projection products. The most difficult factor to control is the brightness of the image. Digital systems use feedback controls that enable the systems to monitor the power supply to the light source, providing consistent light levels to the screen, although it is still necessary to change the lamp after approximately 1000 hours of use. Another key to consistency is the projectors' color calibration technology. Projectors are set up in theatres and their light output is measured with a high quality colorimeter. Native color points are measured and entered into the set-up software; the projector then calibrates itself, modifying the projector color, as needed, into the target DLP Cinema™ color space. This process takes into account environmental concerns such as port glass and screen color that impact image performance. The end result is that projectors in theatres match the projectors in mastering and deliver the same director approved image …quot; from the first screening to the last.