What else is happening before the first curtain on E-M1?

Started Mar 31, 2014 | Discussions thread
Timur Born
Timur Born Veteran Member • Posts: 4,769
Re: Shutter video

Anders W wrote:

It's not hard proof yet, but it's an indication. I don't know if it is possible to download a video from youtube or play it back frame by frame where it already is (it seems not). If we could do that, we could of course verify the timing, but it seems roughly right based on my eyeballing.

This is what the first curtain looks like frame by frame from a 120 fps iPhone video of the E-M1, both with AS0 and without AS. Both times the blades do the same movement of completely covering the sensor.

Anti-shock 0s - clack sound only at the end (image 7)

No anti-shock - clack sounds in the middle (image 4) and at the end (image 8)

But from sound and tangible feeling it seems to me that in case of enabled AS0 the blades are retracted *before* they can hit against the lower edge. Without anti-shock and higher AS settings you get two clacking sounds, one when the blades hit the lower edge and another when they hit the upper edge at the end. Once short release time is enabled (no cocking at beginning), though, the downwards slamming of the FCS induces only rather small vibrations (AS or not), while the upwards slamming still remains. At least that is what my ears and fingertips tell me, but practice seems suggest that the downward slamming still matters.

With Anti-Shock 0s there is a cave-at that might hint to how ECS differs from higher AS settings and how ECS works. AS0 adds a considerable lag between opening the FCS and closing the SCS! You can reproduce this very audibly by switching between 1/320 and 1/400 with AS0 enabled (or turning AS0 on and off at 1/320). Comparing the lag with anti-shock setting longer than 0s confirms that this only seems to happen with AS0.

My guess is that the FCS is only moved to get it into position for firing off the SCS, because that's how the E-M1's shutter is mechanically build to operate (just as Anders already suggested). And since it is not needed for blanking the sensor it's kept close for shorter (not at all) and thus practically braked before hitting hard. Additionally I think that the electronic curtain is only finished (maybe even started) after the FCS already slammed back open and thus adds the additional lag! This would allow the vibration of the FCS slamming upwards to be dealt with as well.

What I would like to see now are comparisons of anti-shock 0s versus higher settings to see how the observed (by me, can be wrong) lag affects images (supposedly positively)?!

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