E-P5 and "shtter Shock"

Started Oct 6, 2013 | Discussions thread
Anders W
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Re: Shock vs. shake
In reply to Andy Westlake, Oct 7, 2013

Andy Westlake wrote:

3DrJ wrote:

In recent threads it was discussed how DPR seemed to obfuscate the issue in the EP5, stating differences when using touch screen vs. shutter button. In other words, if we believe DPR's idea, the source of "shake" that affects images is broader than just the mechanical action of the shutter, thus confusion among camera owners as well as testers.

'Shutter shock' should look like mirror shock on SLRs, and have the same characteristics. Crucially, mirror shock is visible on a tripod, and 100% reproducible shot-to-shot. It's also independent of how the shutter is released (shutter button, remote release, touchscreen etc). This is well known, and it's why most SLRs have a mirror lock-up function.

The phenomenon we observed with the E-P5 does not look this at all. With the camera on a tripod, there's absolutely no hint of blurring, in all the test shots I've taken (which runs into hundreds). This is true not just on the properly-solid tripods I normally use for testing, but also on the lightest, flimsiest tripod I own, which is very wobbly indeed (I wouldn't dream of using the E-P5 on it normally). The shake also substantially goes away if you use the touchscreen to release the shutter when shooting handheld. This doesn't fit a 'shutter shock' explanation at all.

Hi Andy,

I have been interested in the problem of shutter shock for quite a while by now and have done some fairly extensive testing of the problem as it manifests itself with my E-M5.

You claim that placing the camera on a tripod should not reduce the blur if it were indeed due to shutter shock. Could you please explain in physical terms why you think so.

As far as I can see, there are at least two mechanisms that are likely to reduce (though perhaps not completely eliminate) the impact of shutter shock when the camera is placed on a tripod.

First, it reduces the amount of camera body movement required to absorb the momentum of the moving shutter blades. This is weight-dependent and attaching the camera body to a tripod effectively increases its weight (both because the tripod weighs something and because, depending on the rigidity of the tripod, the tripod stands on something that weighs still more).

Second, the use of a tripod increases the likelihood (at least with a short and light lens on the camera, e.g., the 45/1.8 you use for your studio scene) that whatever camera movement remains takes the form of translational rather than rotational movement (vertical shift rather than pitch), where translational movement has the advantage of usually implying far less blur than rotational. See here for a more detailed development of this point:

http://www.dpreview.com/forums/thread/3496076

The shake does substantially go away if you shoot-hand with 1/8 sec anti-shock. It's visible again if you shoot hand-held with a 2 second self-timer, and my impression is that this has often been considered clinching proof of a shutter shock mechanism. The problem is that this comparison changes two variables at once, which any trained experimentalist will tell you is a bad idea. The correct comparison with 2 second self-timer is 2 second anti-shock - and in my testing, shake is (perhaps unexpectedly) similarly visible with both - it comes back again with the longer anti-shock delay. Again, I don't see how this observation can fit a 'shutter shock' mechanism.

The outcome you describe here is indeed mysterious. But if you have problems with unexpected blur even with two-second self-timer or anti-shock, that shows conclusively that the problem is not due to the mechanism you first pointed to in your E-P5 review (the shutter button and the way it is pressed), no?

A few things to keep in mind here:

First, in my experience/testing, the extent to which anti-shock helps at all is strongly dependent on how you hold the camera. If you hold it right (from a shutter-shock prevention point of view), anti-shock will not be of much additional help. If you hold it wrong, it will.

Second, while the first phase of shutter action (shutter closing to prepare the sensor for exposure) is certainly part of the problem and while a sufficiently long anti-shock delay will certainly eliminate that part from the equation, that's not all there is to it. The remaining phases of shutter action cause problems too.

As to the E-P5 specifically, note also that it has another shutter than previous Oly MFT cameras. Since the new shutter allows flash sync at a faster speed (1/320 rather than 1/250), its blades must by definition move at a faster speed than on earlier shutters. Everything else equal, this is a drawback from a shutter-shock point of view since greater speed yields more momentum to be absorbed.

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