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strobing from panning with long lens


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#1 Tom Pollock

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Posted 04 September 2008 - 12:49 PM

I was panning across faces with a 50mm lens and when transfered it looked like it was strobing, can anyone explain why?
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#2 Chris Keth

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Posted 05 September 2008 - 12:07 AM

I was panning across faces with a 50mm lens and when transfered it looked like it was strobing, can anyone explain why?


For the same reason that false motion blur and stretching are used in animation for fast motion.

Your eyes refresh every 1/14th of a second or so. Any time you pan so fast that an object moves in frame more than it's own width in this period of time, it will appear to strobe rather than move.
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#3 Sam Wells

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Posted 05 September 2008 - 12:33 AM

It's sometimes called "retinal skipping" -- caused by the fact the cells sensitive to light on your retina are spaced at around 7 minutes of arc - so if a lateral displacement occurs frame to frame that 'skips' the adjacent row if cells your brain would expect the object to be normally placed on your brain does not interpret the displacement as smooth continuous movement.

A solution: pan more slowly or use a higher frame rate.

-Sam
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#4 Jonathan Bowerbank

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Posted 05 September 2008 - 01:17 AM

You see it a lot in the movie theatre with slow pans of shots that have a lot of vertical opjects (trees, etc.).
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#5 Chris Keth

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Posted 05 September 2008 - 01:38 PM

A solution: pan more slowly or use a higher frame rate.

-Sam


There's also another solution: increase shutter angle. This will increase motion blur which will help tie those strobing objets together into an illusion of motion. It's not the best solution or even a valid option most of the time but I thought I'd throw it out there.
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