[MacDV] Re: The Sony Canon debate

[James Asherman]

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> Ok, not to fuel a debate but this reference is similar to others I 
> have seen.  I'm no video professional and I'm not looking for a fight. 
> I'll let it go with one last description of how I understand all of 
> this works from the perspective of an physics engineer who worked in 
> real-time image processing, IR guided weapons...
>
> I suspect our disagreement comes from our definition of optical 
> stabilization.
> So here is how I use those terms.
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> 1) Pure Electronic Image Stabilization.
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> In this scheme sequential images are numerically/electronically 
> compared. The last image is shifted through by various amounts in both 
> directions until the difference is minimized. This is the image 
> position that is recorded.  In high end implementation, the images can 
> even be resampled and sub-pixel shifts can be evaluated. Obviously 
> this require a lot of computing power but gives astonishing results 
> and very high dynamic response for very high vibration situations. 
> There are no mechanical moving parts which permits the high dynamic 
> response. Because of the amount  of  computing power required, this is 
> mostly for military  applications. The process of matching images is 
> called image registration. This process requires the image sensor to 
> be elarger than the final image size or black bands will appear on the 
> side.
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> 2) Hybrid Image Stabilization.
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> In this scheme, instead of comparing sequential images to measure the 
> jitter, inertial sensors measure the acceleration vertically and 
> horizontally. The acceleration are electronically integrated twice to 
> compute the orientation change. The recent advent of silicon 
> acceleration sensors permit very cheap and efficient motion sensing. 
> Once the motion has been estimated, the image is shifted by the 
> measured amount and recorded. This is the most affordable solution 
> because it still use no mechanical parts and the use of sensors 
> greatly reduce the amount of computing power that needs to be packed 
> into the camera. However the sensors are not perfect and the measured 
> motion is less accurate than method number 1. This also require an 
> image sensor with more pixels than the final captured image to avoid 
> black bands.
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> 3) Mechanical or Gyroscopic Image Stabilization
>
> Here, the entire camera/lens is mounted onto an inertial platform 
> stabilized by gyroscopes, springs and dampers. Typically this setup 
> can also be used to steer the camera and is found in systems from 
> Flir, Wescam, Sonoma Design... You find these stabilization systems 
> under Helicopters, Unmanned Aerial Vehicles, and even mounted on some 
> rails next to Olympic tracks to follow runners. Hugely expansive, but 
> very high performance and provides a steering of the camera also.
>
> 4) Optical Image Stabilization
>
> Here, the camera uses a lens with a moveable optical group or prism . 
> The group/prism can be shifted to counteract the pointing jitter. 
> Typically, sensors (like in method 2) measure the jitter and instead 
> of electronically shifting the image, the optical group is physically 
> shifted to bring back the image on the same position on the sensor. 
> Because of the requirement to physically move the optical group, the 
> dynamic response is limited to lower frequency movements and very high 
> frequency vibrations are not well cancelled. However the image can be 
> shifted by minute amounts (fractions of a pixel) before capture by the 
> sensor and this will generate better image capture. Physically moving 
> elements also consumes more power and is harder on the batteries. This 
> setup doesn't require image sensors to be larger than the final image 
> size.
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> http://www.canondv.com/gl2/f_image_stabilization.html
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> My understanding is that all consumer and prosumer camcorders that 
> announce stabilization use the method number 2 because it is cheaper 
> and gives good enough results. I only know of the Canon GL1 or GL2 
> class cameras that use method 4.

I am already tired of this one but..
VX1000 and TRV900 to my knowledge use type 4. TRV9 too.
type 2 appears to be the regular steady shot.
I think panasonic uses type1. blocky.

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> But then again what do I know ...

me  either.
Jim

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> cheers.
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> PS: the link http://www.digitalvideoforless.com/steadyshot.htm works 
> for me.
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