Image stabilisation

[leica dream]

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Someone remarked to me that one should disable image stabilisation when using a tripod because otherwise it would cause camera vibration.

True or false?

I use a VLUX-1.

 

Richard

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[ho_co]

Richard, that's the general rule.

 

Some manufacturers of interchangeable lenses with built-in image stabilization say in the instructions to turn off IS when shooting from a tripod.

 

I try to remember to turn IS off when using a tripod, but sometimes forget. And in my experience, it doesn't seem to make any difference.

 

I don't know the reason for the recommendation. Avoiding camera vibration doesn't make much sense, does it? But whatever it is, the suggestion is not to use IS if shooting from a tripod.

[mjh]

Someone remarked to me that one should disable image stabilisation when using a tripod because otherwise it would cause camera vibration.

True or false?

True, although the suggested reason is bogus. It depends on the IS (Panasonic’s OIS is mostly well-behaved when the camera is mounted on a tripod) and it also depends on the exposure time; the longer the exposure time the more likely it is that the image stabilizer causes unsharpness rather than preventing it.

[adan]

IS works by moving either part of the lens (OIS) or the sensor itself to compensate for image movement due to shake of the whole lens/camera object. Either the sensor or a part of the lens is actually free to move around when IS is on.

 

If the camera/lens is physically stabilized (tripod), leaving that moving bit free to move is likely to do more damage to the image than help, so turning it off ensures it won't accidentally twitch and blur the image (and also saves battery power).

 

As Howard says - it won't ALWAYS cause movement/blur. But why take the risk?

[leica dream]

That is most helpful, thank you.

The otherwise extensive VLUX-1 camera manual does not mention the effect (or otherwise) with tripods.

Richard

[Your Old Dog]

Some automatic features will "hunt" for something to work on. Your IS "could" start hunting for some movement to correct. That hunting could cause an OOF image. Automatic Gain Control, AGC, is another example of the hunting process. If there is no primary audio for the AGC circuits to work on they bring up the background noise level and you hear the whooosh.

 

I try to remember to turn of IS on my Canon 5D mkii when using the sticks.

[mjh]

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Some automatic features will "hunt" for something to work on. Your IS "could" start hunting for some movement to correct.

No, it won’t do that. It is still a good idea to turn of image stabilization when the camera is mounted on tripod, but for different reasons. This “hunting for camera shake” thing is a myth.

 

Automatic Gain Control, AGC, is another example of the hunting process. If there is no primary audio for the AGC circuits to work on they bring up the background noise level and you hear the whooosh.

That’s not “hunting” either. The AGC is a rather simple mechanism: It increases the gain until a given output level is reached. It doesn’t care about whether the signal getting amplified is really worth amplifying. There’s no useful analogy between an AGC and an image stabilizer.

[ho_co]

Here I have to disagree, Michael. I wouldn't call IS and AGC analogous, but I do understand YOD's point: You're giving control to an automatic processor without being able to predict its behavior. (A very distant analogy.)

 

Remember the "How the M9 is made" video. There were at least half a dozen posts about the crashing noises at the beginning. Some people who didn't recognize the effects of AGC actually seem to have thought there were loud noises going on in the background, where the exact opposite was the case.

 

But in terms of the effect of IS, I agree with you that there is no similarity to the effect of AGC.

 

Perhaps you could tell me this: I've read that in-lens IS will occasionally reset, and that that's the reason it should be disabled on a tripod. I've never seen this happen when I'm using an IS lens manually and doubt the accuracy of the statement; it sounds as if it's another version of the "hunting" argument.

 

To your knowledge, is there any validity to the claim that in-lens IS will occasionally "rethink" and cause a jerk?

[mjh]

Perhaps you could tell me this: I've read that in-lens IS will occasionally reset, and that that's the reason it should be disabled on a tripod. I've never seen this happen when I'm using an IS lens manually and doubt the accuracy of the statement; it sounds as if it's another version of the "hunting" argument.

 

To your knowledge, is there any validity to the claim that in-lens IS will occasionally "rethink" and cause a jerk?

Not that I know of. It seems people are attributing far too much intelligence to the IS – it doesn’t actually rethink its actions, it doesn’t hunt for camera shake, and neither does it (and I’ve heard that, too) get crazy ideas when the camera is mounted on a tripod and the IS starts wondering why there is no camera shake …

 

The reasons why the IS should be turned off are twofold. For one thing, the IS is optimized for a certain range of frequencies, say 10 to 20 Hz or thereabouts. It isn’t very effective against very slow movements, partly because the gyro sensors used to measure camera movement aren’t perfectly calibrated – there may be some very slow camera movement that goes undetected or the sensors might report slow camera movent that isn’t actually happening (because the camera is mounted on a tripod). For the exposure times the IS is optimzed for this error contaminating the signal from the gyro sensors doesn’t really matter; the movement that goes uncompensated or the falsely reported movement that is compensated are too slow to make a difference – and in any case the damage done is much smaller than the positive effects of the IS. But the error will have an effect with long exposures when the IS wouldn’t do much good anyway, so it should be turned off in those cases.

 

The other reason is this: The IS takes the input from the gyro sensors, predicts the way the camera will move within next couple of microseconds, and moves a lens group to compensate for that predicted movement – the compensation will take full effect by the time the camera has reached the predicted position. If the IS algorithm is any good, these predictions will mostly be spot on, but sometimes they will be off the mark and in these rare cases the IS will add rather then avoid motion blur. Normally the good predictions will outnumber the mistaken ones so the net effect will be positive. But if the camera is mounted on a tripod, whenever there is camera movement predicted by the IS we know it must be mistaken since the camera doesn’t actually move. There cannot be any positive effects while the wrong predictions still occur and the net effect is motion blur induced by the IS. It is not like the IS was less effective on a tripod or that it would be more likely to make errors; it is just that its normal error rate isn’t offset by the correctly predicted camera movement it perfectly compensates for.

[ho_co]

Thank you very much, Michael!

 

Clear and concise as usual!