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Old January 25th, 2008, 09:24 PM   #1
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What happens when shutter is off?

I just got my EX-1 yesterday, and had a shoot today (with another camera) so haven't had too much time to play, but I have a question which may be a silly one. When the shutter speed is set to off, what is happening? Is it resulting to a fixed shutter speed (if so what....say if I am at 1080/24p). Normally I set my shutter to 1/48 at 24p and when shutter is off the image becomes brighter indicating a lower shutter speed yet the motion still looks like 1/48 and not 1/24, which is what I suspected was happening. So what is happening with shutter off?

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Old January 25th, 2008, 11:07 PM   #2
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"Shutter off" sets your shutter speed to your frame rate, so at 24p it's 1/24 second.

Or, to put it another way, shutter off sets a 360° shutter.

As far as I know, there is no way to set you shutter speed to 1/24 in 24p except by turning it off.

There really is no shutter in the camera, and so all the switch it doing is changing the camera's internal settings. It's not really turning anything on or off. The switch is just an interface choice by Sony for something that could have been accomplished in the menus.

Shutter speed is the delay between resetting and reading the CMOS sensor. At 1/48, for example, the camera clears the sensor (resets) to let it start accumulating light energy and 1/48 second later reads the amount of light accumulated. With the shutter off, the camera just waits longer (the full time alloted to the frame) to do the read cycle.

As a side note, because it's a "rolling shutter" camera, these operations do not happen in an instant, but scan down the image. The amount of time that it takes to do these scans has been measured at 1/60 second.

Last edited by Eric Pascarelli; January 26th, 2008 at 09:36 AM.
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Old January 26th, 2008, 12:57 PM   #3
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Assume that the shutter is off and several flash pictures are taken.

I would expect that if we go through the footage frame by frame, with 24p some frames would have the flash for the full frame and some would have the flash on the bottom half, then on the top half of the next frame.

NOTE: 1 ms (millisecond) = 1/1000 of a second

With 24p, each frame is 41.7 ms and 1/60 of a second is 16.7 ms.

Thus, 41.7 ms - 16.7 ms (open) - 16.7 ms (close) = 8.3 ms (20% of the time) where the whole frame is being exposed and 16.7 ms + 16.7 ms (80% of the time) while the "shutter is moving".

Another item is when shooting 720@60p, chances are that a flash will appear with the bottom half exposed and the top half in the next frame. I don't have an EX-1 to see how that appears, when playing back, but it sounds like an interesting test.

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