CN writes:
<<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.
EFC is not instantaneous and is about 1/10 to 1/15 I've seen with GM-1/5. In
general with mechanical curtains the faster the first curtain, the faster the
sync speed and all things being equal more shutter shock
in mirrorless---witness E-P5 with horrible Shutter Shock. (second curtain must
follow at same speed to keep exposure even) Perhaps the whole procedure is
different with EFCS and flash but I don't see how one can get a sync speed of
1/50th w/o some tricks. (why I let questions like this gnaw at me, I don't
know) GM-1 goes to 10 bit when going to total e-shutter and can clear the
sensor in 1/25 sec. Interestingly Oly chose in E-M5II to stay 12 bit RAW with
EFCS and clear it in 1/20--a very good compromise. That can still result in
rolling shutter artifacts and banding in some light like fluorescent.
Oh, here is some data on GM-1.
http://www.dpreview.com/forums/post/53300241
Still not seeing the light in EFC with flash, Mike
--
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