On Sharpness, ISO and Shutter Speed

Started Nov 29, 2013 | Discussions thread
Steen Bay
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Re: On Sharpness, ISO and Shutter Speed
In reply to Anders W, Dec 1, 2013

Anders W wrote:

Steen Bay wrote:

Anders W wrote:

Steen Bay wrote:

Anders W wrote:

Steen Bay wrote:

Anders W wrote:

Ken Strain wrote:

These data are puzzling, two features disturb me most:

The spread between H and V gets to about 20% in several of the plots, including the points for the EM5 at 1/4000s. I am reluctant to accept that particular case as being due to shutter shock. If those data are bad, how can we tell which are good?

The EM1 plot is the only one that looks somewhat like I would expect if shutter shock were the main cause of the spread, but even here it appears that something else breaks the H-V symmetry with the opposite sign (such that there is roughly 6% discrepancy between the averaged H and V scopes of the 3 fastest speeds).

Hi Ken,

To me, the graphs for the E-M5, the A7R, and the D610 are pretty much in line with what would be expected in the presence of shutter shock, not just that of the E-M1. Of course, there may be other reasons for a difference between vertical and horizontal resolution too, as strongly suggested by the graphs for the D610 and A7.

A bit strange that the blur is mostly vertical with E-M1 and A7R, and mostly horizontal with D610.

You are right about that. I overlooked that it was the horizontal rather than vertical resolution that dipped in the critical range in this case. And I guess the D610 shutter (which is what distinguishes it from the D600 and its problems with dirt on the sensor) is moving vertically just as the other ones.

Seems that a good, heavy tripod isn't enough to prevent blur at certain shutter speeds, so could be interesting to know which shutter speeds are used by Photozone, Lenstip, DxO, SLRgear, etc. when testing lenses. Can we trust the results from cameras known to be affected?

Yes. The same thought has occurred to me. What I hope is that they prefer not to have more light in the studio where they do this than they really need, and that they therefore shoot at shutter speeds where shutter shock ceases to be much of a problem (although its effect may not be completely gone), like at 1/20 or below.

Guess it's most likely that the lighting is constant and that the shutter speed changes with the f-stop, like it changes with the ISO in DPR's studio scene.

That would be my guess as well.

At least SLR Gear are aware of the problem as you can see from their recent review of the new Pany 14-140 here:

http://slrgear.com/reviews/showproduct.php?product=1611

Yes, and that's with a 250 pounds tripod!

Yep. Although I suspect that there is something special about this lens and other Power OIS lenses with, as it seems, similar problems (X 14-42, X 45-175).

Yes, seems that the amount of blur will vary not only from camera to camera, but also from lens to lens, and also depends on the tripod, tripod head, hand helding technique, etc. It's rather complex.

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