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From: Mailbag: HD Movies and the resolution of film : Home Theater Blog | Home Theater News & Reviews

• The resolution of the movies shown in theaters

And now to answer your last question, “What is the resolution of the movies shown in theaters?” This one isn’t as easy to answer because well, there is no fixed answer. Film stock isn’t bound by the same rules that make up the pixels in a frame of video. Most of the data I’ll cite from here on out comes from a great study done by the International Telecommunications Union, specifically sub-group 6 which deals with large screen digital imagery. Their study titled ‘Image resolution of 35mm film used in theatrical presentation’ is as close to the definitive word as I’ve found on the subject.

One thing to keep in mind is that analog film has no ‘lines of resolution’ as we know them in the video world, but it is possible to arrive at a comparative resolution by using a resolution-chart in the frame that equates to fixed video resolutions.

The study indicated a 35mm negative has a resolution in excess of 2400 lines by picture height but obviously we don’t watch negatives, the film has to be processed into a stock reel. Those tested stock reels were found to have a maximum comparative line resolution of 1400 lines P/H, still considerably more resolution than 1080p’s vertical integer. (Note: the P/H formula is used because film has the same vertical and horizontal resolution, where video does not.)

Luckily the study also included real-world data collected at a sampling of movie houses. I say luckily because no matter how good the film stock, the theater’s equipment plays just as much into how the projected image looks as the film itself.
This part of the study only reinforces my anticipation for high definition DVD as the numbers indicated what we’re seeing at the theater in many cases falls short of 1080p. The study indicated a comparative, average line resolution of between 685 lines and 875 lines P/H. But again don’t let these numbers alarm you as the film stock itself is more than capable of bettering HDTV, it seems it’s the movie houses that have been letting us down.