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Electronic first curtain operation?

Doug Kerr

Well-known member
Canon notes that the newly-announced EOS 1D X body provides "electronic first curtain" operation, not previously available in the "!" series.

I believe this mode is used as part of one or more of the "silent" shooting modes of, for example, my EOS 40D.

As I understand it, in this mode, the optical (physical) shutter is opened before the shot is commenced and, in effect, the CMOS sensor is "reset" to establish the beginning of exposure.

The exposure is, I believe, ended with the closing of the second curtain of the optical shutter.

Now, the second curtain takes a substantial period to close, "wiping" across the frame as it does so.

Since we want a consistent exposure time across the frame, I assume that in electronic first curtain operation, the reset of the CMOS (or at least the "release" of the reset) must also move progressively across the frame, with a time profile intended to mimic the travel of the second curtain.

Do we know if this is so? And if not, then how is consistent exposure time across the frame accomplished?

Thanks.

Best regards,

Doug
 

Doug Kerr

Well-known member
Well, duh!

The 40D White Paper says:

With Live View Function image displayed, the 40D can shift seamlessly to slit exposures with the electronic 1st-curtain shutter, enabling silent shooting which is not possible with a mechanical 1st-curtain shutter. This electronic 1st-curtain shutter uses a unique high-speed scanning and electronic reset system that accurately mimics the EOS 40D's high-speed mechanical shutter operation. It synchronizes with the mechanical 2nd-curtain shutter to obtain a slit exposure. (Note that with CMOS, it is difficult to have an electronic 2nd-curtain shutter. Therefore, only the 1st-curtain shutter is electronic.)​

Aha! Just as I suspected!

I note their use of the term "mimic(s)". Ah, great minds . . .

Greater minds read the reference material first, of course!

Best regards,

Doug
 

Cem_Usakligil

Well-known member
Hi Doug,

interesting question, which got me to do some web search. You have found your answer in the meantime, my search has delivered the same answer. This website and also this one seem to contain relevant info on this.

Cheers,
 
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