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This answer mentions that CMOS sensors "cannot" use digital shutters where as CCD sensors can. Even if some models have the ability to, it is certainly typically for CMOS sensors to use mechanical shutters instead. Why might this be?

Preamble: I ask with a particular problem in mind. My mirror-less camera uses a CMOS sensor and has an electronic view finder. When the shutter is half pressed (exposure is calibrated, focus is set, the EVF frame-rate increases) the video image seems nigh on identical to the photo. The sensor is clearly able to accurately process a stream of light hitting the sensor into images without a mechanical shutter, so why is a digital shutter off the cards? As far as I can see the mechanical shutter wastes battery, obligately creates an audible noise, takes time to shut-open-shut-open, and makes the camera thicker and heavier.

This boils down to what is the advantage of a mechanical shutter in mirrorless CMOS cameras?

  • Panasonic GX7 have CMOS sensor and electronic shutter – Romeo Ninov Dec 27 '14 at 18:19
  • @RomeoNinov I had a sneaky suspision that some may be able to do this. I've tweaked the question, but I suspect CMOS had to overcome a technical barrier to achieve CCD style electronic shutter, although I don't know what that barrier was. Regardless it is still atypical for CMOS to use electronic shutters and I want to know why. – James Dec 27 '14 at 18:36
  • seems like this is the problem CMOS and CCD sensors work. I am not very good in microelectronics, but maybe this document can help you: onsemi.com/pub/Collateral/AND9195-D.PDF – Romeo Ninov Dec 27 '14 at 18:50
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There are CMOS-based cameras with electronic shutters (basically all cameras with video mode have electronic shutters) but the technology does have its limits.

When the camera reads from a CMOS sensor it reads the data line-by-line, not all at once, this means that, if the subject or the camera moves fast enough you can get very interesting effects.

CCD sensor, on the other hand, dumps the content of the entire sensor into a second set of components that are not exposed to the light, the camera can then read the "frozen" image.

Video uses the electronic shutter because:

  1. there's less data to read — so the camera can read it faster (full HD is about 2 megapixels, 4K is more difficult at between 8 and 9 megapixels)

  2. camera designers don't have a choice, a mechanical shutter that can run at 60FPS without breaking will be expensive

For still photos a mechanical shutter is still better.

Note: there are cameras that use the electronic shutter to begin the exposure and the mechanical shutter at the end of the exposure

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    A mechanical shutter is also "rolling". Take a picture of an airplne propeller at 1/4000 and behold the moving slit. – JDługosz Sep 1 '15 at 5:22
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I have a Panasonic G5 with electronic shutter. The electronic shutter is a rolling shutter, The electronic shutter is open for about 1/10 seconds for fast shutter speed. Sometimes you can handhold without noticing the distortion, but if you pan a shot the distortion is obvious. The electronic shutter cannot be used with flash. The slowest shutter speed is 1 second.

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