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by evan-pak

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Are there any cameras with built-in technology to detect that the main subject is still and then take the picture?

Suppose I have three kids in focus, in close range (assume small room) and I would like to take a picture of them when every one of them is still and not moving.

Do we have technology like this?

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Welcome to PhotoSE @otti. Interesting question. I am not sure what you want to achieve with this, however. Are you getting blurry pictures because the kids are moving so often even when you ask them to be still? Or are you just inquiring about the possibility of camera figuring a still moment by itself and shooting? – Regmi May 15 '13 at 19:40
I would like the camera to figure out a still moment and Shoot. – otti May 15 '13 at 21:31
A lack of motion sensor? Seems like something that would be extremely challenging to put into a camera, just consider how much of the world is not actually in motion and how accurate your focus would have to be to not include that in the decision process. – John Cavan May 16 '13 at 2:41

Yes, there are plenty of machine vision systems that will tell you if an object is moving.

I'm not aware of any cameras that implement it since it's computationally expensive (that's to say requires lots of processing).

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Many cameras have focus-priority, where they will not release the shutter until focus is achieved, but I don't know any that will block the shutter release if the focus is acquired, but the subject is in motion. Never mind doing this for multiple subjects.

Nikon has a motion detection feature in some cameras that detects subject motion and increases shutter speed, but that's a poor substitute.

The Nikon 1 series also has a feature to take a number of shots in rapid succession, so you can then review and choose the optimal one. I think something like that is your best bet at present.

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I do believe that type of technology would be irrelevant in a camera as all you need to do to freeze action is increase the shutter speed.
You may also need the help of a flash to go along with the increased shutter speed.

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Flash is not required. – otti May 15 '13 at 21:32
@otti: He means, that if you increase the shutter speed, the picture gets darker (all else constant) so at some point (after maxing out ISO and Aperture) you will need flash to illuminate the scene. – Unapiedra May 15 '13 at 22:10

I have seen the opposite behaviour in a cheap security camera system. It can be set so it records only in the event of movement in the field of view of the camera, when there is no movement, the frame rate drops to save storage. It seems to do so by comparing two succesive frames and if it detects difference among the frames it records all the frames, otherwise, it only records one frame every two seconds.

This particular camera does not have anything tha could "detect" movement by itself, it only has the lens and a few IR emitting diodes. The movement detection feature can be defeated, for example by walking straight towards the camera (since it produces very little variation from one frame to the next). Walking across the field of view, in the other hand, triggers the recording mode almost inmediately.

Is my guess that a camera with liveview, or a camera with face recognition can be programmed on a similar principle. Such a feature could be practical for the kind of user who preffers to shoot in automatic all the time. The logic is fairly simple, the camera "sees" many frames, and when it detects enough of them that do not change, picks any of them to record it as a picture.

Another application of such logic could be for example to take pictures of landscape or cityscape automatically removing any moving objects, like passing cars or people. It would work as a very long exposure comprised of many "frames". The "frame difference" algorithm would be used to drop any frame that "does't fit" and after enough time, the camera would produce a picture of "everything that was still".

Indeed such simple algorithms would have numerous drawbacks, and possible would need fine tuning of parameters to suit them for particular situations, thus rendering themselves useless for the "automatic user". Besides, even a user of exclusively the auto modes can produce good results by making small adjustments, so everything is reduced to a market decission: there may not be enough buyers of the feature to make it a profitable selling feature.

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