4 ms·

It boils down to higher effective shutter speeds. Barring a global electronic shutter (such as was in the Nikon D100 and D70 CCD cameras), you can get much fast

It boils down to higher effective shutter speeds. Barring a global electronic shutter (such as was in the Nikon D100 and D70 CCD cameras), you can get much faster shutters (or, really, lower exposure times at the sensor) with a focal plane shutter than you can with a leaf shutter. The limiting factor is not how much stuff you can move how far in how little time, but how narrow you can make the moving slit. Not only does a leaf shutter need to fully open and fully close to create the exposure, it needs to do it quickly enough to have a negligible effect on the len's aperture (both for exposure and for depth of field control reasons). That speed does come at a cost, though, since there is a point at which you cannot expose the entire sensor at once. (That's also true of rolling electronic shutters, by the way.) Flash needs to be worked around in various ways, and anything moving in the frame will suffer distortion. I still have good reasons to use an old Nikon in some circumstances (lower resolution requirements, high ambient light levels and flash). While they do have focal plane shutters, they only go up to 1/250 of a second. Faster than that and you're using a global electronic shutter, which doesn't reduce effective aperture when the lens is wide-open or nearly so, but still expose the entire sensor in one go. That means I can use a higher shutter speed to control the ambient exposure while using very low flash power. That means no waiting for recycling or carrying around large amounts of lighting equipment.

mark-r 9y ago
Aren't there modern sensors that have electronic shutters? Why isn't this capability found on newer cameras?
- maxxxxx 9y ago
  Electronic shutters don't work well with fast moving objects. You can get distortion. I think they don't read out the whole sensor at once.
  - stan_rogers 9y ago
    The global shutter on the Nikon 6MP CCD sensor was really global, not like the rolling electronic shutter on a CMOS sensor. You got an all-at-once still, the electronic equivalent of a leaf shutter; the current scanning versions are basically a "no moving parts" version of a traditional focal plane shutter.
- oakwhiz 9y ago
  It's usually called a global shutter, and it adds complexity to the sensor design, because each pixel has a tiny amount of "memory" with a gate and capacitor to store charge into. There is a signal bus that simultaneously moves all the charges from the constantly exposing pixels into the storage areas, where the charge is no longer being increased by exposure, and can be read out asynchronously using a switching matrix and a bank of ADCs. This avoids the problem where the charges of the pixels you haven't read are still increasing through light exposure.

mark-r 9y ago

Aren't there modern sensors that have electronic shutters? Why isn't this capability found on newer cameras?

maxxxxx 9y ago
Electronic shutters don't work well with fast moving objects. You can get distortion. I think they don't read out the whole sensor at once.
- stan_rogers 9y ago
  The global shutter on the Nikon 6MP CCD sensor was really global, not like the rolling electronic shutter on a CMOS sensor. You got an all-at-once still, the electronic equivalent of a leaf shutter; the current scanning versions are basically a "no moving parts" version of a traditional focal plane shutter.
oakwhiz 9y ago
It's usually called a global shutter, and it adds complexity to the sensor design, because each pixel has a tiny amount of "memory" with a gate and capacitor to store charge into. There is a signal bus that simultaneously moves all the charges from the constantly exposing pixels into the storage areas, where the charge is no longer being increased by exposure, and can be read out asynchronously using a switching matrix and a bank of ADCs. This avoids the problem where the charges of the pixels you haven't read are still increasing through light exposure.