On 6/30/2010 1:49 PM, Chuck Norcutt wrote:
> Umm, as I view that video
> <http://www.dpreview.com/reviews/olympuse520/page7.asp> it seems to me that
> the E-520 very much drops the mirror even in Imager AF mode.
>
They were there, and presumably could hear/feel whether the mirror
dropped. I have no reason to mistrust them. My experience of cameras
I've had is that their tests are remarkably through and accurate.
All mirrorless digicams have a blackout of video feed between the time
the shutter is pressed and the time the processed JPEG is displayed on
the LCD screen. It's inherent in current technology, which requires a
reset of the sensor and mechanical shutter operation for still shots.
Still cameras with the ability to capture a still frame during video
capture have a brief lacuna in the video when the still is taken for
that reason (1 sec. on the 5DII). Pure video cameras don't, at least
mine doesn't, as it simply captures a frame from the stream, but that's
because the sensor system is different.
Certainly all mine have had blackouts of various length. With the G11,
it is quite brief, but certainly there. With early digicams, it was
sometimes tediously long. It's possible it isn't visible on the screen
with short shutter speeds on some cameras with fast processing.
In the case of a DSLR, , the focal plane shutter usually has to close
then open-close to capture the image. The usual process is that the
shutter closes, the sensor is reset, the shutter is re-cocked, opens and
closes for the exposure, then the second curtain is re-cocked with first
curtain open for LV and second curtain open, ready to start the next
cycle. The close, re-cock, expose, close cycle must briefly cover the
sensor twice. So two blackouts of video feed from sensor for LCD screen
occur.
> The E-620 seems to behave differently. There's no blackout period.
> <http://www.dpreview.com/reviews/olympuse620/page8.asp>
>
The 5DII has alternate LV "silent shooting" modes that use an electronic
shutter, whatever that is, to eliminate the first close-open cycle for
sensor reset. That would eliminate the first shutter related blackout.
If processing of the JPEG for screen viewing is fast enough, the second
curtain blackout might not be visible. Remember, by default, unless you
change it, the first thing seen after the shot is taken is the captured
image, not live feed.
Perhaps the E-620 is doing something similar. Hard to tell from the
static DPR test subject. You'd think 1/20 sec, plus curtain travel time
would show on the video, but if the video frame rate of the screen is
slow, it might not.
It could also simply hold the existing screen image for moment, to cover
the blackout, a cosmetic solution. Oly will never tell. One could try
testing by taking a long exposure on an E-620. IF the LCD blacks out
during the actual exposure, the lack of blackout on shorter exposures
may be simply fast image processing. If it doesn't black out, they are
'cheating'.
In any case, shutter operation does mean at least one, and usually two,
breaks in sensor availability for live image feed to the LCD, even if
the mirror doesn't flap.
Moose
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