On Sharpness, ISO and Shutter Speed

Started Nov 29, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Another possible experiment

ProfHankD wrote:

Anders W wrote:

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?

Two things:

  1. As I said, I personally have not seen blur from play in a lens, but displacement from frame to frame. (Theoretically, if it were just vibration, then there shouldn't be any displacement from frame to frame.)
  2. The "another possible experiment" I suggested, that started this thread, would resolve at precisely what points in the exposure cycle displacements happen.

But doesn't point one suggest that the displacement of whatever it is that is displaced happens between rather than during any given exposure, in which case it wouldn't really be relevant in the present context (that of specifying the reasons for blur)?

Of course, I don't know if the lenses DPReview tests with have any such issues. I don't see any way to be sure of the cause of the blur just by examining the DPReview comparison images.

No. I don't think we can be sure of the cause of the blur just by examining these images either. Further tests, which only DPR themselves are in a position to carry out, are most likely required.

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