Hi, Bought a Z50 ii recently, felt that I got a little rolling shutter when using the Auto setting for shutter type so set it for Mechanical. Was out photographing some terns today and got massive distortion from what I assume is rolling shutter on several pictures. Is this to be expected?
I'm not sure everybody understands what "rolling shutter" is.
A focal plane shutter consists of two curtains, a front curtain which is closed before exposure and a rear curtain that is open before exposure.
The time taken for the front curtain to open fully is short, generally with a mechanical shutter one can determine this time by looking at the maximum flash sync speed. Often this is 1/250 second.
When the shutter is released the front curtain starts to move, depending on the shutter speed selected (doesn't matter how it is selected) the rear curtain starts to close some time later. At. shutter speeds below the flash sync speed the rear curtain doesn't start to close until after the front curtain is fully open. Thus at 1/60s the front curtain starts to open and 1/60s later the rear curtain starts to close. The whole area of sensor gets exposed for 1/60s but one end gets exposed slightly earlier than the other.
At shutter speeds higher than the flash sync speed the front curtain starts to open as before but, before it reaches fully open, the rear curtain starts to close. Thus the rear curtain follows behind the front curtain. The higher the shutter speed the more closely the rear curtain follows the front curtain. Effectively there is a slit between the two curtains
rolling across the sensor. Hence the term "rolling shutter".
It is important to realise that ALL focal plane shutters that rely on two curtains have rolling shutters, it cannot be avoided. Hence the interest in global shutters where the entire sensor is exposed at the same time.
To explain the visual effect of a rolling shutter, let's imagine a fast moving subject travelling from left to right across the field of view. The leading edge of an aircraft's wing for example. With the shutter closed the front curtain moves downwards. As it starts to move the wing is to the left of the frame, as the curtain travels downwards the wing is moving to the right. By the time the front curtain reaches the bottom of the frame the wing is further to the right than it was when the exposure started. hence instead of being rendered as straight it is curved. The rear curtain follows the front curtain.
Note: The property is present whether the shutter is mechanical or electronic. I have mentioned the sync speed for a mechanical shutter because it is somewhat easier to understand and describe.
adapting-camera.blogspot.com
