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Re: [OM] Paging Moose, re. Shutter shock

Subject: Re: [OM] Paging Moose, re. Shutter shock
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 19 Apr 2015 13:52:47 -0700
On 4/19/2015 12:23 PM, Mike Gordon via olympus wrote:
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.

That's not how it actually works. When using a mechanical second curtain, pressing the shutter release starts a process of clearing the existing data on the sensor a row at a time, at a speed to match the speed of the second curtain, in effect mimicking a mechanical first curtain. Once the second curtain has closed, the whole image is read.

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.

The GM1 uses EFC up to 1/500, then fully electronic to 1/16,000 (yup, three 
zeros)

  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.

Yup, that's how it works

Roll Out Moose

--
What if the Hokey Pokey *IS* what it's all about?
--
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