Originally posted by m42man Yes, the reason behind the delay is somewhat puzzling. However, my take on it is as follows:
1. Finger off shutter button. The sensor-positioning control system uses sensor-position sensors to hold the platter in the "nominal" position, ready to take a shot. The vibration sensors aren't being used yet.
2. Shutter button halfway depressed. AF takes place, but I don't see why the SR mechanism has to do anything different at this stage. Are we saying that we're not allowed to recompose - especially after the hand appears?
3. Shutter button is fully depressed. I would have expected that here the camera inserts a very short delay in order to allow the SR mechanism to switch from the sensor-position sensors to the vibration sensors as its reference. Then the mirror flips and the shutter is fired, and during this period the vibration sensors tell the SR control system where to position the platter.
So why do we have to wait for the hand symbol? My thought was that in (1) above, the camera might limit the current available to the SR mechanism, to save power. Then it would need some time to maybe reposition the platter more accurately during (2). But this would imply that the camera consume more power when SR is turned off, which seems very unlikely.
So what's really going on while we wait for the hand? Anyone have any definitive knowledge?
At point 1, the image sensor (platter) isn't positioned at all, it lays loose at the bottom of it's well free to move around if you tilt the camera. The famous "clunk" noise can be heard if you tilt the camera.
At point 2, the accelerometer sensor activates and starts measuring the background shake frequency and amplitude, also a sort of general direction builds up. When all necessery data is collected the hand lits up, you should not recompose unless you stay in the new composition for 0.7s before you fire.
The platter is still loose and no power is feed to the positioning servos.
At point 3, the mirror starts flipping and the positioning servos powers up and moves the platter from wherever it is to its calculated position and, hopefully, moves in sync with the background shake and also ready to counter any movement from the general direction built up during the 0.7( or so )seconds before the shutter was pressed. Now the shutter blades opens.
If you fire before the SR system is ready (hand is not lit) the mirror flips and the positioning servos lift the platter to its center position and holds still, exactly as is it would do if the SR system was shut off.
When people claim that the SR ruined their shot because it wasn't ready, I bet it really was because they changed their aim right before they fired and the SR tried to counter it. I call it user error.
However, the K5 have changed the SR system behavior in that it does stay active as long as the metering is active (you don't have to hold the shutter half pressed). Also notice if you now recompose when the hand is lit, the light goes out showing that the data collected is thrown away and a new 0.7s cycle is started collecting data in the new direction.