We digitize movie film pixel by pixel
 Q: How are movie films and old records converted to digital recordings? --Michael M., Cincinnati,
Ohio
A: This--the first of a two part answer- tells how we digitize movies. Next week's column addresses how
to digitize old vinyl records.
[Corel] A graphic filmstrip
Movies and photographs record latent images by the action of light on a film. Subsequent development (chemical treatment) makes
those latent images visible.
Digitizing the image is simple: a scanner examines the film for light and dark areas and also for color (whose components are red, green,
and blue). The scanner records a corresponding binary number (a series of 0s and 1s) for each minute area of the original image; it
records a greater number for lighter areas than for darker ones. Each number represents a picture element (called a pixel) consisting of
one or more tiny dots treated as a unit in the resulting digital image. The scanner creates three separate versions of the image to capture
color: one for each of the three primary colors of light.
While scanning in the film data, the restorer pre-processes the film. He crops the digitized picture to obtain only the image portion, then,
rotates and shifts it so it looks right in comparison to adjacent frames. He sizes the frames as necessary and adjusts the image
brightness. Then he stores the pre-processed images.
"While single images can fit onto a CD, entire films tend to be recorded on hard disk or digital tape formats," says Eef Masson of the
Filmmuseum in Amsterdam, Netherlands.
Then the restorer tackles the main job--correcting flaws, cracks, blots, and color degradation.
A major reason for film restoration (apart from physical damage) is dye fading and color loss, Masson says.
Finally the restorer has the film on a hard disk, digitized and the images corrected to their original harmony of form and color. He has
brought back the past from slight film traces.
(Answered by April Holladay, science correspondent, December 19, 2001)
Further Surfing:
How stuff works: scanners
Filmmuseum, Netherlands: programs
Tokyo U. Digital Museum: Digital film restoration of "Tokyo Story"
PC Tech Guide: Digital imaging
Computer Friends, Inc: How scanners work
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