On Sharpness, ISO and Shutter Speed

Started Nov 29, 2013 | Discussions thread
Anders W
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Re: Another possible experiment
In reply to ProfHankD, 11 months ago

ProfHankD wrote:

Anders W wrote:

This prevents the camera from being displaced but not from vibrating. Result: No sign of blur. So at least in this case, brute displacement rather than vibration is the cause.

Well, I've never trusted tripods as much as bracing on part of a building anyway....

For what it's worth, even with everything bolted to a concrete block, many cameras do suffer from what you're calling physical displacement.

Well, I meant displacement of the entire camera rather than parts of it (as in your example below). In my example, we know that vibration is not the mechanism because there is no blur when displacement of the entire camera is prevented. In your example, vibration can be involved since you get blur even when displacement of the entire camera is prevented.

Obviously, we cannot rule out the possibility that the results of my experiment, using a particular lens on a particular camera, does not generalize to other cases. What it does show is that you can get blur due to shutter action that is not mediated by vibration but by displacement of the body as a whole.

One possibility that we are discussing with regard to the DPR studio scene samples at issue in this tread is that the problem might be due to something being slightly loose in the particular specimen of the lens used. See here:

http://www.dpreview.com/forums/post/52627215

One suprising thing about these particular samples is that they are presumably shot on a heavy studio tripod, which ordinarily should prevent the camera as a whole from being displaced to any significant degree due to shutter action. Furthermore, the FL used isn't very long, which should also limit the amount of blur due to any remaining displacement of the camera as a whole.

For example, bolting-down a camera and taking a series of non-blurry images, many camera+lens combos (even without mechanical image stabilization) will not quite have images align at the pixel level. The culprit there is apparently play in the lens system, which can be made much more visible if the system tries to focus for each shot, but can be induced by things as simple as the whack from the aperture stop-down lever on Sony A-mounts. Old (high-mass, tight-tolerance) manual lenses don't seem to have this problem at all.

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