Film Grain in Postproduction – Bringing Texture Back
A form of postproduction that can be applied to CinemaDNG files is film grain. For some, the idea of shooting in raw reflects in some ways an approach to filmmaking that harkens back to the days of working on film. What is lost in digital filmmaking involves the loss of texture. Film grain is one way to help bring texture back to the filmmaking process. Filmmaker Michael Plescia discusses this below. Take note of the stills and how they exemplify Plescia’s argument about film grain (see “Digital Bolex D16 Downtown LA Test Shoot” at https:// vimeo.com/74438041).
Michael Plescia Discusses Adding Film Grain in Postproduction:
My recommendation: grain in your post pipeline while the image is flat, so that the grain acts as a dithering mechanism allowing for color corrections that can be much more aggressive in the DI. Also, by doing so, you avoid weird color banding and color blocking that I’ve seen in badly color-corrected RED footage. Footage originated on film is grained from the beginning because grain is the image which helps dither any non-linear color correction curves and that’s why film shot images can be pushed to such degrees of saturation and richness—where digitally originated footage usually falls apart. (Notice how The Girl with a Dragon Tattoo and many RED shot films excel with very desaturated grades.)
I degrade the image slightly with a post-applied “optical blur” filter on a base layer (What!? Blurring HD resolution footage and making it effectively less sharp?) I do this in a compositing package to take away things like too-sharp skin pores or leaves in the background and then I use a grain pattern scanned from neutral grey 16mm film stock as a track-matte that acts as a screen or a sieve that allows areas of the sharp, non-degraded HD footage through in speckles.
So this helps mimic the effect of “dancing resolution accumulated over time.” In other words the skin pore that hangs on the face in Digital Bolex and Ikonoskop footage does not appear on all frames although I should mention that these cameras lack of compression gives the footage inherently much more of this dappling effect already.
This type of more aggressive graining, for the looks I love, also has further benefit in the pipeline because as the final film goes through compression algorithms for bluray, Vimeo, YouTube etc., the compression schemes that look for uniformity over time, like H.264 algorithms, have more difficulty finding blocks of uniform image to simplify—especially in the lowlights where information is often thrown away.
By “stumping” the compression schemes that hunt for information to throw away, it becomes more difficult for the algorithm because it cannot as easily identify and hold steady blocks of temporally consistent patterns over multiple frames and the algorithm can’t hold a key frame of compression over subsequent frames. The first thing YouTube and Vimeo compression algorithms do is see if they can lower the data rate allotted to a given video by degraining the image, so I always like to have my grain intensity at a level so that YouTube can’t declare my black levels meaningless.
Again, I argue that in the grain of the blacks exists such an important component of the aesthetic experience in genres like horror, art films, thrillers etc. Overall, when you compare a frame of Vimeo or YouTube compressed video where on one version you “confused” the algorithm with this type of grain and on another version you did not (given the data rate is the same), you will see the grained version looks to be of much less quality because the algorithm is struggling and distributing its same data rate over the entire image.
I actually like this look better and would argue that your eye is actually “seeing” more depth over time than in an image where the lossy algorithms had their way. I’d rather spend it over the whole image rather than letting the algorithm decide that the actor’s blackheads are the fine detail that should be preserved.
Excerpt from Cinema Raw: Shooting and Color Grading with the Ikonoskop, Digital Bolex, and Blackmagic Cinema Cameras by Kurt Lancaster © 2014 Taylor and Francis Group. All Rights Reserved.
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