Color grading
Color grading is a post-production process common to filmmaking and video editing of altering the appearance of an image for presentation in different environments on different devices.
The number of points per stop varied based upon negative or print stock and different presets at film labs.
After the session, the timer would return to the lab and put the film negative on a device (the Hazeltine) which had preview filters with a controlled backlight, picking exact settings of each printer point for each scene.
These settings were then punched onto a paper tape and fed to the high-speed printer where the negative was exposed through a backlight to a print stock.
For complex work such as visual effects shots, "wedges” running through combinations of filters were sometimes processed to aid the choice of the correct grading.
As explained by Jay Holben in American Cinematographer Magazine, "The telecine didn't truly become a viable post-production tool until it was given the ability to perform colour correction on a video signal.
"[2] In a cathode-ray tube (CRT) system, an electron beam is projected at a phosphor-coated envelope, producing a small spot of light.
Once this photon beam passes through the film frame, it encounters a series of dichroic mirrors which separate the image into its primary red, green and blue components.
From there, each individual beam is reflected onto a photomultiplier tube (PMT) where the photons are converted into an electronic signal to be recorded to tape.
Today there are many companies making color correction control interfaces including Da Vinci Systems and Pandora International.
Secondary grading can isolate a range of hue, saturation and brightness values to bring about alterations in hue, saturation and luminance only in that range, allowing the grading of secondary colors, while having a minimal or usually no effect on the remainder of the color spectrum.
Color tints can be manipulated and visual treatments pushed to extremes not physically possible with laboratory processing.
Inside and outside of area-based isolations, digital filtration can be applied to soften, sharpen or mimic the effects of traditional glass photographic filters.
From 2010, many films, such as Hot Tub Time Machine and Iron Man 2, began using the complementary colors orange and teal.
The first full digital intermediate of any form was the Cinesite restoration of “Snow White and The Seven Dwarves” in 1993 (previously, in 1990, for Rescuers Down Under, the Disney CAPS system had been used to scan artwork, color and composite it, and then record it to film, but this was also intermixed with a traditional lab development process over a length of time).
Their real time performance was optimized to particular resolution and bit depths, as opposed to software platforms using standard computer industry hardware that often trade speed for resolution independence, e.g. Apple's Color (previously Silicon Color Final Touch), ASSIMILATE SCRATCH, Adobe SpeedGrade and SGO Mistika.
The line between hardware and software no longer exists as many software-based color correctors (e.g. Pablo, Mistika, SCRATCH, Autodesk Lustre, Nucoda Film Master and FilmLight's Baselight) use multi processor workstations and a GPU (graphics processing unit) as a means of hardware acceleration.
