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I am a little confused about the concept of shutter speed in video shooting mode. I assume that the "shutter speed" means how fast the shutter would open and close. When this happens, I would hear a click sort of sound from the camera which means that shutter was opened and closed. My question is, how does shutter work when shooting movies? Is it opening and closing constantly? If so, why do I NOT hear any sound indicating that shutter is working? Does "hearing nothing" mean that shutter is wide open during shooting a video?
On the other hand, however, I think the frame rate should be related to the number of times that shutter gets opened and closed in a second. So if we are shooting a video at 24 fps, I expect 24 shutter movements in a second. right? Am I missing something?

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Should be migrate here. –  Itai Sep 20 '12 at 16:50

1 Answer 1

up vote 9 down vote accepted

The shutter you hear is a mechanical shutter and it cannot on a DSLR move fast enough to shoot at video speeds which is between 24 and 60 FPS. High-end mechanical shutters usually top at 12 FPS.

The shutter used in video and high-speed drive on some cameras is an electronic shutter. There are no moving parts involved and hence no sound. The sensor simply discharges itself at regular intervals.

The issue with electronic shutters is that they cannot make the sensor stop being sensitive to light, so while it is being discharged, some light still gets accumulated. Mechanical shutters are still being used to avoid this happening with stills. For video we just put with the consequences, namely vertical streaking for CCDs (because CCD rows are discharged by shifting into the next ones) and jello-effect for CMOS (because each row is read at a different time).

Things are a little more complicated actually because video has a frame-rate (24 FPS to 30 FPS) and a shutter-speed (which maxes our at 1 over the frame-rate, so 1/24 for 24 FPS). So you may be shooting 24 FPS video in bright light with a 1/1000s shutter-speed, meaning that the frame is read after 1/1000s but the sensor is cleared via the electronic shutter after 1/24s for the start of the next frame.

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Would the RED cameras be an example of a mechanical shutter like you speak of? –  dpollitt Sep 20 '12 at 18:04
    
@dpollitt - RED dont use a mechanical shutter... However Arri's D21 camera which uses a CMOS sensor does have a shutter. –  Darkcat Studios Sep 21 '12 at 8:37

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