Monday, April 26, 2010


We were at a restaurant the other night in Oakland, SR24. It's one of those nice places that's sort of hip. It had an HDTV over the bar playing 2001: A Space Odyssey, off a Blu-Ray disk, I'm assuming. They clearly had the "Motionflow" screen interpolation setting on, as it looked really "fake".

Of course it didn't really look "fake". It looked "hyper-real", as if you were in the same room with the events. But why does that look fake? The hover text of this XKCD cartoon explains it:

If you hover the mouse over the image you get this:
We’re also stuck with blurry, juddery, slow-panning 24fps movies forever because (thanks to 60fps home video) people associate high framerates with camcorders and cheap sitcoms, and thus think good framerates look “fake”.

A movie, of course, is made up of a strip of still images. The projector light flashes 24 times per second showing us 24 still images per second. Our brains can't discern it though and see it as a fluid moving image. But we discern more than we think.

Standard old-school North American TV's show 30 frames per second. But on TV's it's a refresh rate. The image refreshes 30 times per second. It doesn't blink on and off. Movies have to be adjusted for TV which is why they never look quite the same as on the big screen. It's also why video cameras where built to shoot at 60fps: it's divisible by 30 and doesn't have to be adjusted.

Modern 120Hz HDTV's can refresh 120 times per second. 120 is divisible by 60 and 24. This allows movies to show without being adjusted, except that it repeats the same image 5 times every 1/24 of a second.

Unless you have the screen interpolation setting on, which basically fills in the extra frames to make it look "smoother".

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.

In 1789, the governor of Australia granted land and some animals to James Ruse in an experiment to see how long it would take him to support himself. Within 15 months he had become self sufficient. The area is still known as Experiment Farm. This is my Experiment Farm to see how long it will take me to support myself by writing.