Panasonic Electronic Shutter - How Does It Mimic Shutter Speeds

TedGamble

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I have read several articles regarding Panasonic's electronic shutter.

I understand that the system scans the sensor to capture the image. I have read that it takes 1/10 second for a full sensor scan. Sooooo, if it takes 1/10 sec to scan the sensor, how does the system accomplish shutter speeds of less than that. For example, how does it mimic 1/500 sec?
 

brettmaxwell

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it may take 1/10s to scan the whole sensor, but each pixel only records light for 1/500s (or other set value). That's why it's called a sensor scan, think of a flatbed scanner, it starts at one side of the frame, records all those pixels for 1/500, moves down/across the frame, records the next row or rows of pixels, and continues until it has scanned all the pixels. For this reason, if you shoot with an electronic shutter out your car window you will see all the vertical lines are slanted. This is because the car has moved and the scene has changed in the 1/10s between when the first rows of pixels were scanned and when the last rows were scanned.
 

kwalsh

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What Brett said.

And keep in mind this is exactly what a mechanical shutter does as well at speeds faster than the flash sync speed. So, for instance, when you shoot a mechanical shutter at 1/4000 a second what actually happens is a slit moves across the frame and takes roughly 1/250th a second to go from top to bottom.
 

T N Args

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this is exactly what a mechanical shutter does as well at speeds faster than the flash sync speed. So, for instance, when you shoot a mechanical shutter at 1/4000 a second what actually happens is a slit moves across the frame and takes roughly 1/250th a second to go from top to bottom.
Just thinking out loud --- doesn't this mean that mechanical shutters have exactly the same rolling shutter effect as electronic, but at 1/250 instead of 1/10 sec? (given the examples quoted) -- and hence less obvious but still present?
 

TedGamble

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So, in reality, we're referring more to pixel "read" time more than the actual time the entire sensor is exposed? I had no clue that the mechanical shutter worked that way. I was assuming the curtain came down, the entire sensor surface goes into "read mode" and the shutter curtain slices its window across the sensor.

In retrospect, what I was imagining for mechanical shutters is more of the "global shutter" paradigm (which is to yet become a reality)?

Thanks for the clarification. It all makes sense now.
 

T N Args

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The reason mech shutters have a 'speed limit' is due to the time it takes for the curtain to traverse the sensor. This might be 1/250 sec. So, for faster than 1/250 sec (in this example), the second curtain has to start its trip before the first one is finished.
 

kwalsh

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Just thinking out loud --- doesn't this mean that mechanical shutters have exactly the same rolling shutter effect as electronic, but at 1/250 instead of 1/10 sec? (given the examples quoted) -- and hence less obvious but still present?
Exactly.

In fact if you remember in cartoons from the past speeding cars are often depicted with oval tires. This mimics the rolling shutter effect of very slow mechanical focal plane shutters of 4x5 cameras used by most press photographers of that era. It was common for portable press cameras to use focal plane shutters instead of leaf shutters in the lens itself as most studio camera of the era did. The Speed Graphic is the classic camera of that era with a focal plane shutter. So the cartoon animators drew speeding cars to match the appearance people were used to seeing in news paper photographs of speeding cars. This is akin to the present day when CG'd scenes add lens flare effects to mimic what people are used to seeing from actual lenses...
 

RRRoger

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So, am I now confused?
Sounds like the only advantage of an electonic shutter is silence.

When I recently tried to use my GH3 at a MotoCross Event the results were so much less than steller
that I thought it was the 14-140 lens which had worked OK for Video.
I have it set for silent mode with electronic shutter because I mostly use it for indoor Video.

But, evidently I should change it to mechanical shutter for Action Stills?
 

dhazeghi

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So, am I now confused?
Sounds like the only advantage of an electonic shutter is silence.
It eliminates shutter shock. That can be a big difference at certain shutter speeds.

When I recently tried to use my GH3 at a MotoCross Event the results were so much less than steller
that I thought it was the 14-140 lens which had worked OK for Video.
I have it set for silent mode with electronic shutter because I mostly use it for indoor Video.

But, evidently I should change it to mechanical shutter for Action Stills?
For subjects that are moving at substantial speeds, the mechanical shutter is preferable.
 

brettmaxwell

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Sounds like the only advantage of an electonic shutter is silence.
the GM1 electronic shutter takes over after 1/500, which presumably allowed them to use a smaller and/or cheaper mechanical shutter.
additionally, it can go to 1/16,000, which is really great when you're shooting fast primes in daylight.
 
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