Film - A Practical Guide to Video and Audio Compression - page 47

adequate resolution for IMAX at the time. It would result in a raster size of approximately
4096

2854. Taking film grain size into account, the theoretical maximum for this format is
approximately 8192

×

5944. The picture size of the image on the 70 mm film stock is approx-
imately 69.6 mm by 48.5 mm. Taking that size and the pixel dimensions into account, a
scanning resolution of 115 pixels per mm or 2920 pixels per inch is derived. At an 8K reso-
lution, each pixel would be about 25 mm square on the screen surface of a 215-meter wide
screen.
Scanner manufacturers have standardized some popular resolutions regardless of
the technology they use. They are based on the number of pixels scanned across the image
area, regardless of its size, and they tend not to discuss dots per millimeter.

×

2K (2048 pixels across)

●

3K (3072 pixels across)

●

4K (4096 pixels across)

●

6K (6144 pixels across)

●

1536. It's commonly
referred to as “2K,” but of course that doesn't describe any aspect ratio or anamorphic
scaling. It is an industry standard, however. At 2K, the results look a little soft and fine
detail gets lost. To compensate for this, some companies work at 4K resolution, with its
attendant increase in storage and file sizes. The 6K resolution is considered to be as high
as the industry is prepared to go for normal projects; due to the massive increase in data
sizes, it's only used for the largest projects.
At a 2K working resolution, fine detail in hair is resolved quite poorly. The 4K reso-
lution solves this, and even if the final output is reduced to 2K, the difference is still appar-
ent. This high-resolution scanning and subsequent “down-rezzing” was developed by
Cinesite as part of the digital intermediate process and is known as Super 2K.
The 6K scanning resolution is sometimes used to pull a single still frame image off of
the film so that it can be used in book projects. These tend to be photoset at very high res-
olutions, and they therefore can benefit from the denser scanning.
Table 4-1 suggests some alternative scanning densities based on conversations with
manufacturers of telecine systems and film scanners.
Choosing the right scanning density is crucial to achieving the best possible quality.
The resolution depends on the grain size of the stock and the image size being scanned.

The normal working resolution for digital film projects is 2048 ×

Table 4-1 Some Examples of Scanning Resolutions

Description Resolution

IMAX on a 4K scanner 58 dpmm

IMAX on a 8K scanner 115 dpmm

VistaVision on 4K scanner 109 dpmm

16 mm frame on 2K scanner 212 dpmm

16 mm film full width including sound track on 2K scanner 128 dpmm