E-P5 review updated with look at anti-shock

Started Oct 7, 2013 | Photos thread
lester11
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Not the shutter press AFAICS
In reply to Andy Westlake, Oct 8, 2013

Spent a happy few hours, finally got my E-M5 to show its shutter shock. Got my E-PL3 to show it earlier, that was quite easy, here is before (no anti-shock) and after (anti-shock set at 1/8 sec) with the 45/1.8 at 1/60 and f4. You can easily see the double image vertical ghost:

E-PL3 45/1.8 1/60 sec f4, left no anti-shock, right 1/8 sec anti-shock

Could only coax shutter shock out of the E-M5 with the 60/2.8 macro at 1/80 and f4.5, here it is without the grip on the body. Before (no anti-shock) and after (anti-shock 1/4 sec), again the clear double image vertical ghost:

E-M5 60/2.8 macro 1/80 sec f4.5, left no anti-shock, right 1/4 sec anti-shock

But here is the point of this post. I put the grip on the E-M5 and took shots vertically, ie portrait orientation. This is the science bit, so concentrate (smile)... (If I've got any of this wrong, I'm sure y'all will straighten me out immediately.)

Blur comes from a variety of vibration sources, and can be defined to be a generalised smearing in both dimensions of the image. Shutter shock is a kind of blur (a) in only one dimension, and instead of smearing it manifests (b) as a ghost image, as shown by the example snaps above. In the above snaps, the shock acts vertically exclusively such that all horizontal edges are double imaged with ghosts while no vertical edges are ghosted. And, there is no smearing, just ghosting.

That's why the camera has two settings to combat vibrations. The common "release delay" of 2 secs or 10 secs is to let vibrations damp out and avoid smearing-type blur. The relatively new "anti-shock" is to let a quite different vibration damp out and avoid double image ghosting.

When you press the shutter release button, the sensor is first blanked off completely to the lens and electronically discharged. Then, the first curtain opens and is followed by the second curtain to give the exposure. If you set "anti-shock" and make it, say, 1/8th, then the camera waits 1/8 sec between closing the sensor and firing the first curtain.

The curtains fall vertically when the camera is held horizontally in landscape orientation, so that the curtains, and the aperture slot, move from top to bottom, sky to earth so to speak. My understanding is that the curtains fall in the same way even if you hold the camera vertically in portrait orientation, and in this case the curtains and the aperture move horizontally across the image, left to right.

Most folks think the shutter shock comes from the initial shutter action when the sensor is blanked off, and that the sensor is (or the curtains) are still vibrating from that shock when the first curtain opens. Other folks have other explanations, and Andy and the DPR Team think it is due to your finger pressing down the shutter release button and transmitting that to the sensor.

Let's imagine that it was my finger pressing the shutter button down which caused the double ghost image. This is plausible, and is consistent with the finding that the double image ghost is vertically displaced. But the vertically displaced double image ghost could also be due to the initial shutter action closely followed by the first curtain falling vertically.

So let's put the grip on the camera, turn it to portrait orientation, and use the grip's portrait shutter release button to fire the exposure. What should we see?

If it is indeed my finger causing the problem, the double image ghost should still be seen as a vertical displacement when we view the resulting image. My finger was, after all, pressing down. On the other hand, if the problem is the shutter action itself, then the double image ghost should now be displaced horizontally.

Here is the result:

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--Lester

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