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Beyond HD
Although most theatrical films in the U.S. today are still primarily shot with 35mm cameras and projected from film prints, the route to the theatres is starting to change. Many film projects, high budget to lower budgets, will go through a digital intermediate process before being printed out to film. In addition, many films are being shot today with various HD cameras and are then printed out to film for theatrical release. The latest digital advancements have also brought higher-end digital cameras and projectors into use that have resolutions higher than that of HD, even uncompressed HD. Here is a brief rundown on some of the terms associated with this new and quickly expanding frontier.
Digital Intermediate: (DI) This term originally is used to describe digitizing film at a high resolution (2K or 4K), performing all post production needs like effects and color timing digitally, then printing out to film. The DI is the digital negative in a sense, the intermediate stage between the original film and the final film print. Today, DI's are also used for films shot on digital video cameras, SD, HD and newer digital cameras with higher resolution than HD.
2K: Describes a horizontal resolution of 2048 pixels. Scanning full-frame 35mm film produces an image size of 2048x1556. 2K is today the most common DI scanning resolution, as well as post production workflow, incorporating 2K projectors, 2K capable color correction suites and effects workflows.
4K: Describes a horizontal resolution of 4096 pixels. Scanning full-frame 35mm film produces an image size of 4096x3112 (or 4096x3072). 4K, although 4 times the area of 2K, is not yet as widely used throughout the entire post production pipeline. Digital 4K cameras and recorders are starting to become a reality, notably with the Dalsa Origin camera (4096x2048 frame size) and Codex Digital, a digital recorder capable of recording 2K, 4K, and 4:4:4 uncompressed signals. A new camera stirring up a lot of buzz is a new digital 4K camera called the RED camera. Additionally, 4K projectors are becoming more common, making the leap to 4K more of a reality.
The output frame size of either a 2K or 4K scan will vary based on the aspect ratio being used. In the above descriptions of 2K and 4K scan sizes, the example used is for a full frame 35mm negative, which has approximately a 4x3 aspect ratio, a square-like frame size. When outputting a 1.85:1 aspect ratio, for example, there will be less vertical resolution (less horizontal lines) than a full frame negative because it is a widescreen format. And an aspect ratio of 2.35:1 will have less of a line count than 1.85:1. So, in practice, 2K only defines a horizontal resolution of 2048 pixels, and 4K defines a horizontal resolution 4096 pixels, but as we just saw, vertical resolution depends on the final aspect ratio, which will undoubtedly be less than the numbers described above for a full frame 35mm negative.
Cineon: Developed by Kodak. The Cineon file format was designed for scanning film for digital film work like effects, digital color timing and the creation of digital intermediates. It is an RGB bitmap10-bit log file that corresponds to the density of the film negative, preserving the original gamma. It can hold an exposure range of approximately 11 stops. Support for up to 16-bit depth per channel.
DPX: (Digital Picture Exchange). File format used in high end applications like film scanning for use in digital film work, like effects, digital color timing and creation of digital intermediates. 10-bit log file preserves image densities similar to Cineon format. Standardized by ANSI/SMPTE 268M-2003. Similar to the Cineon file format except that DPX can store more header information and image data information. This format has become quite popular lately for this type of high-end digital film work.
OpenEXR: File format developed by Industrial Light and Magic (ILM). Currently in use on all films at ILM. High dynamic range format supports 16 and 32-bit float point as well as 32-bit integer pixels. Supports multiple lossless compression algorithms.
HD D5: This tape deck is discussed in more detail in HD Tape Formats. The reason to include it here is that there is an optional 2K processor enables 12-bit, 4:4:4 recording in 1920x1080 or 2K (2048x1080). RGB or XYZ color space. 188 Mb/sec bit rate.
RED One: The first 4K camera introduced by the Red Digital Cinema Company. The camera records files to a mountable hard drive called a RED Drive, a RED Flash drive or to Compact Flash cards. The recording format is a RAW based format called REDCODE, which is a 12-bit wavelet based codec. Because the format is natively RAW, when viewing images through the viewfinder or a monitor on set, the image seen is not true to the image that is being recorded. The image that is viewed is being given a "look" through various choices the user is given. But the look is only temporary and when the images go to post production, that look can be stripped off and taken in another direction. If a look was not applied during the viewing, the image would look very milky and flat as the camera is recording an incredible wide latitude of luma and chroma information. It is best equated to a film negative, which has a wider range of information then the final film print and can be printed in a variety of ways. The final look is not "baked" into the RED RAW images as they are recorded similar to a film negative, giving the final colorist a wide range of options for the final processing of the image. Another interesting note about the RED One camera- it uses a Bayer pattern sensor to record red, green and blue information, but records twice as much green information as red and blue. In order to watch a "viewable" image, the RED images need to be de-bayered, a process that can be intensive for computer software to handle. There is also a hardware based option from RED that allows for real-time de-bayering. The RED One camera records 4K, 3K and 2K images, in frame rate options that span from 23.98 up to 120 fps (depending on the frame size). In all sizes, the user can choose different aspect ratios, either 2:1 or 16x9 (1.78:1).
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