A Staff Report from the Straight Dope Science Advisory Board

What is the maximum resolution of photographic film in pixels?

December 31, 1999

Dear Straight Dope:

Last night I was watching the latest computer graphics extravaganza to come out of Hollywood. As I watched the list of credits for the computer graphics houses (which took longer to scroll by than the movie did) I started wondering: What is the theoretical maximum resolution in "pixels" for photographic film? What about 70mm and 35mm movie film? What is the practical resolution of the picture seen on the big screen? What is the resolution on the computer picture that gets printed to film?

SDStaff Gry replies:

The easy answer to your question is that there is no maximum resolution in pixels for photographic film. Pixels are a computer thing. You know that a pixel is a dot, right? We measure screen resolution for computer monitors in pixels because electron guns "draw" each dot on the screen and this is what makes the picture appear. The smaller the dots, the more you can pack in per square inch and the greater the detail they can convey. Film doesn't work this way. A film image is created not by dots but by blobs of colored dye with continuous gradations of tone. (OK, film does exhibit a characteristic known as "grain," but don't get technical on me.) When projecting film, a light is shone through the film and the blobs of color show up on the screen. No pixels involved.

Aas for the resolution of a computer picture printed to film —  it's usually about 1600dpi (dots per inch). Incidentally, that's about the resolution of the photos you see printed in your finer magazines, except that in the print world it's ppi (points per inch) instead of dpi.

Staff Reports are written by the Straight Dope Science Advisory Board, Cecil's online auxiliary. Though the SDSAB does its best, these columns are edited by Ed Zotti, not Cecil, so accuracywise you'd better keep your fingers crossed.

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