Discussion in 'Casual Photo Conversations' started by https://www.blvdartists.com/, Nov 6, 2017.
If IS works, the image should not move when you move the camera.
That is the whole idea.
I don't think that's the idea.
I'm not sure what you mean when you say, "the image should not move when you move the camera." When you make a 180-degree pan, of course the image moves. When I shoot a handheld shot of the moon with IS engaged, of course, the moon moves within the VF, because I can't hold the camera perfectly still. IS slows down any camera movement, such that instead of shooting at 1/500-sec., you can shoot at 1/125-sec. Make a short, handheld video and the subject will still move in the frame, but the shake will be greatly reduced by the IS, such that handheld videos are now watchable, if not as good as when taken on a good video head and tripod.
When I took the following handheld shot of the move, I took several shots. In each frame, the moon was in a slightly different position in the frame. I take over 100,000 handheld shots per year, so I have a lot of practice at it. Anyway, I can tell you, that IS doesn't stop the subject, even a stationary subject, from moving in the frame:
Waxing Gibbous Moon (Explored) by David Stephens, on Flickr
IS is based on motion detection in the camera and/or lens, and not of the subject. Accelerometers measure motion in several directions, causing optical elements (or the sensor) to move in compensation.
It is possible that simple devices like smart phones and P&S cameras use "digital" image stabilization, based on subjects in the image. AFIK, this technology is not used in DSLRs nor MILC cameras. I suspect that digital stabilization does not have the flexibility, resolution nor responsiveness demanded by serious photographers. Among other things, it is based on position, rather than acceleration, which is much more sensitive to small changes and in effect, anticipates the effect of camera shake.
If sensitivity is limited to acceleration, then the motion detectors are not subject to drift when stationary. Mass accelerometers are pretty close to ideal in this respect. Early IS used gyroscopes or oscillators, which are subject to precession, hence drift in static situations.
Interestingly, our own eyeballs have the same kind of image stabilization. In physiology it is called the vestibular ocular reflex. When you fixate on a target, a movement of your head to the right, for example, will be detected by the semicircular canals in your inner ears and a compensating leftward movement of your eyes will help to keep the image of the target stabilized on your retina. I wonder if the engineers who developed IS were aware of that nature already designed a similar system?
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