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

Started 9 months ago | Discussions thread
tt321
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Re: Shutter video
In reply to Anders W, 8 months ago

Anders W wrote:

radsaq wrote:

Anders W wrote:

radsaq wrote:

If the shutter is cocked and then reopened immediately before the sensor is reset, doesn't that mean the entire process could be done in the same time that a normal shutter cycle occurs? The shutter will normally be waiting some number of milliseconds in the cocked (closed) state to let the sensor reset happen before it opens. As far as we can surmise, it's not, and so that has effectively freed up that same interval to be used for the same step, just in a different order. Right?

I would hope you are right but I am not so sure about that. I don't think the first mechanical curtain really needs to wait for the sensor to reset, at least if they've programmed things optimally from the beginning. It will take the mechanical shutter about 1/320 s to close its first curtain (since that's about how fast the blades can move on the E-M1) and in order for the EFCS to sync with the second curtain, the sensor must have the capability to reset within the same interval.

We also have the observations to which I link below from another thread:

http://www.dpreview.com/forums/post/53418777

So a slight delay compared to mechanical shutter only (but less than the 1/8 s minimum of earlier anti-shock settings) seems likely at this stage. That said, I'll be more than happy if anyone can prove me wrong.

Here's a comparison of the sound of two 1/160s exposures in manual/MF with IS off. The EFCS is on top:

Looks like it's an additional 25ms of shutter lag?

Aah, many thanks for that! Very nice test and very nice results! As I said, I would have preferred to be proven completely wrong, but a delay of only 25 ms comes close enough for me to be happy. That's only 20 percent of the minimum delay previously available with anti-shock (125 ms) and with close to complete rather than partial blur elimination!

Two follow-up questions:

1. Is the zero-point on your time scale an absolute one, i.e., does it conform exactly to the time when the shutter button is fully depressed? If not, is there any way you (or anyone else) can manage a test that let us see the absolute shutter lag times (time between shutter button pressing and actual exposure)?

I am thinking here not only or primarily about the impact of the EFCS (where we now know we need to add about 25 ms) but also of the short release lag-time setting. One thing that still puzzles me is that Imaging Resource couldn't see any effect of that setting in their measurements and even claimed that it sometimes increased the lag slightly. See here:

http://www.imaging-resource.com/PRODS/olympus-e-m1/olympus-e-m1A6.HTM

Nearly the same story on the E-P5 where they (probably incorrectly) speculated that the short lag time setting was accomplished by means of EFCS:

http://www.imaging-resource.com/PRODS/olympus-ep5/olympus-ep5A6.HTM

2. I have seen claims to the effect that when operating in high-speed burst mode, where the camera (E-M1 as well as several others) does not provide live view and does not do AF between shots, it no longer has the mechanical shutter do double duty (close-open-close-open) but single duty (open-close). Given that we now know that the E-M1 (and probably its predecessors too) cannot use the second curtain only but must go through all four phases before starting another cycle and given that the curtain opening for exposure must sync with the one closing for read-out, this would have to be accomplished as follows using the abbreviations listed:

FCC - first curtain closing

FCO - first curtain opening

SCC - second curtain closing

SCO - second curtain opening

First shot in the burst: FCC-FCO-SCC

Second shot in the burst: SCO-FCC

Third shot in the burst: FCO-SCC

Fourth shot in the burst: SCO-FCC

If this is true, one could test it by fast panning when shooting with fast shutter speeds with narrow opening (1/4000, for instance). Every shot would have vertical lines leaning in a different way to the next.

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