On 2/8/2010 3:47 AM, Carlos J. Santisteban wrote:
> Hi Ken, Nathan, David and all,
>
> Ken Norton wrote:
>
>
>> Years ago I predicted electronic stabilization using overscan techniques.
>>
> And has been used extensively on videocams -- with much less resolution
> needed.
>
This seems to me to be sloppy thinking.
Overscan stabilization on video works in a fundamentally different way
than for still images. No stabilization is applied to any individual
frame. Rather, individual frames are larger than the output size and are
aligned with each other in internal, streaming "post", then cropped to
the final output image size.
To do this with still images, each "exposure" would need to be sliced
into several much shorter sub-exposures. Certainly not doable at any but
very slow shutter speeds with mechanical shutters - and the noise and
wear!. Even when that is overcome, there are sensor issues to be
considered. When you slice a 1/2000 sec exposure in to multiple small
slices, how does the sensor get enough light in each one to respond well?
Hmmm. I suppose it could be applied only to slower shutter speeds, with
each composed of a series of 1/1000 second slices, for example. Still,
Sensor reading/resetting would have to get way faster than it is today.
Again, video is fundamentally different, using relatively slow shutter
speeds and not caring about subject movement blur. Take a look at
individual frames of 35mm movie film or a video. Lots of movement blur
in individual frames that blends nicely into the desired moving image.
I'm not saying it's impossible, but that it is so with current
technology. Even then, will it be better? Video is viewed in a quite
different way than stills. What's sufficient for images flickering by at
20-30 frames per second with lots of subject movement blur may or may
not be so for a single image that is viewed for several seconds.
Consider that the technique may be in use not for inherent IS
superiority, but because it's good enough and cheaper, being all
electronic processing, than mechanical solutions of moving lens elements
or moving sensor.
A. Skeptical Moose
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