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Author Topic: micro 4/3s  (Read 6597 times)  bookmark this topic!
KeithB
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micro 4/3s
« on: August 06, 2008, 02:53:15 PM »

Does the micro 4/3's include a shutter?

I assume that your typical digicam doesn't have a shutter either - it does it all electronically.

Bob, do you have any opinion as to whether a shutter is more accurate than not having one?

[Also, maybe you should just start a discussion topic for each article you write - or even a separate area of the forum - for those of us with questions.]
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Bob Atkins
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Re: micro 4/3s
« Reply #1 on: August 06, 2008, 11:12:19 PM »

I don't know if micro 4/3 says anything about shutters. Since nobody has ever built a micro 4/3 camera, we can't tell!

The spec really just defines the geometry, a flange to sensor distance of 20mm. I suppose it's up to the camera maker to decide whether or not they want to use a mechanical shutter. For reasons of cost and since they are talking about using Live View for the viewfinder and for focusing, a mechanical shutter seems superfluous since it would have to be open most of the time anyway.

I've heard it claimed that a mechnaical shutter can yield lower noise images since it allows the sensor to be in the dark right up until the moment of exposure. I don't know how true that is, but it sounds like it could have some basis in fact. I believe it is a fact that a mechanical shutter can reduce blooming (charge leakage) from bright (overexposed) areas in an image.

Of course a mechanical shutter can also protect the sensor from "gunk" falling on it when the lens is removed. This isn't an issue for P&S cameras since you can't remove the lens, but it could be for micro 4/3 camera bodies.

Adding a discussion thread directly to each article would require more database programming than I'm anxious to do right now. Maybe just a link to a forum discussion thread might not be a bad idea on some articles though.
« Last Edit: August 06, 2008, 11:19:15 PM by Bob Atkins » Logged
KeithB
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Re: micro 4/3s
« Reply #2 on: August 07, 2008, 08:35:21 AM »

I am thinking that a shutter simplifies sensor design, and might allow for more image area vs wiring.

If you have the luxury of closing the shutter, zeroing out the photosites, opening the shutter, closing the shutter and then reading the photosites at your leisure, you can scan by rows and columns without any concern for speed.

Without a shutter you must zero each photosite (all within a hundred microseconds or so), wait for the exposure time and then read all the photosites within that same hundreds of microseconds.  This strikes me as a difficult problem.  I know that memories read their all thier cells in sub-nanosecond times, but here we have a lot of analog circuitry that needs time to settle among other things.
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Bob Atkins
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Re: micro 4/3s
« Reply #3 on: August 07, 2008, 10:20:53 AM »

True, but in the desgin specs of micro 4/3 they specifically say that AF is done by contrast detection in a Live View mode. Without any reflex mirrors, they can't use seperate AF sensors, so just for the AF they have to have the sensor exposed all the time. I can't see how that could really be integrated with a mechanical shutter. You'd have to use the sensor for AF, then close the shutter, wait for everything to settle, then open and close the shutter and read out the data. You could do it, but I don't know how much delay would be involved and if it would be worth the effort. They also make a point of the video capability of the format, which obviously requires an electronic shutter.
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