I don't see how flash sync shutter speed has any bearing on the amount
of time the EFC takes to clear the sensor. Clearing the sensor takes
place before the EFC shutter is considered open. Then it's open
(instantly), the flash and ambient exposure occurs and the second
curtain closes.
What's odd about the EFC is that the sensor clearing time should place a
limit on the shot-to-shot delay time in the same way that a 1/8 second
shutter shock delay means you can't possibly go faster than 8 frames/sec
minus the shutter speed time for each exposure.
The other oddity (and I really don't know how this is handled) is the
disparity in exposure times from top to bottom with electronic first
curtain but mechanical second curtain. If the EFC is instantly open
then the exposure starts evenly across the entire surface of the sensor.
Yet, when the mechanical second curtain closes, the exposure drops
unevenly across the surface as the curtain starts covering the sensor
from top to bottom or bottom to top (whichever way the curtain moves).
This is probably immaterial for long exposure times (relative to curtain
travel time) but not immaterial for fast shutter speeds. Perhaps that's
why EFC is not used at higher speeds. Or maybe EFC is not instantaneous
but rather it enables rows of pixels across the sensor in a timed,
rolling wave at the same speed as the mechanical first curtain. I don't
know.
Chuck Norcutt
On 4/18/2015 11:39 PM, Moose wrote:
Another effect of EFCS is banding with panos but seems to be technique
dependent and perhaps SS--I move way too slow for that to occur in
general doing panos. No flash allowed either in Sony or Oly but
somehow Panny enabled flash sync of 1/50 with GM-1/5. I don't know
about GX-7 but suspect not. I don't know how Panny pulled that off
with a sync speed faster than the EFC can clear data. Any idea?
Flash fires, second curtain closes, with no more light falling on it,
the sensor state is fixed; lots of time to read it out?
Q & A Moose
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