On Sharpness, ISO and Shutter Speed

Started 11 months ago | Discussions thread
Anders W
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Re: Another possible experiment
In reply to ProfHankD, 10 months ago

ProfHankD wrote:

Anders W wrote: Well, I meant displacement of the entire camera rather than parts of it (as in your example below).

I understood you meant of the camera as a unit, but to me the difference between vibration and displacement is that one has a periodic component while the other doesn't. I haven't seen vibration due to play in the lens, just displacement -- which is why I mentioned it. Probably not the prime cause in the DPReview images -- more often a problem with cheap kit zooms -- but this could explain some of the anecdotal stories we're hearing.

How can you in practice, in the present context, distinguish between vibration inside the lens and displacement inside the lens as a cause of blur?

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.

Agreed that a defective lens could do a world of harm. It could even be something as simple as an intermittent electrical contact or power drain that makes a lens focus/aperture drive motor twitch.

One suprising thing about these particular samples is that they are presumably shot on a heavy studio tripod

I don't trust tripods to be solid at all frequencies. They certainly have harmonic frequencies at which they will vibrate, so an impulse that would only cause minor displacement could easily drive vibration of a tripod that magnifies the problem.

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