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How does mechanical shutter work?
I understand that the shutter curtain opens say top to bottom, then closes again from top to bottom. Does the next photo alternate direction? Does the shutter begin moving from bottom to top. And then on the next photo top to bottom again?.

Or does it return to the top after the shutter closes to prepare for the next exposure?..

Comments (6)

Buzzphotos wrote:.

Or does it return to the top after the shutter closes to prepare forthe next exposure?.

Typically, yes..

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #1

Buzzphotos wrote:.

I understand that the shutter curtain opens say top to bottom,.

Let's say top to bottom..

Thencloses again from top to bottom..

No, bottom to top..

Does the next photo alternatedirection?.

No.

Or does it return to the top after the shutter closes to prepare forthe next exposure?.

Yes..

Actually, I did not read specifically that, per se, but if you look at explanations about flash sync, it's the only way it makes sense...

Comment #2

Devnull wrote:.

Buzzphotos wrote:.

I understand that the shutter curtain opens say top to bottom,.

Let's say top to bottom..

Thencloses again from top to bottom..

No, bottom to top..

NOPE ... he was actually correct with his first statement..

There is actually TWO "curtains"; (a holdover term from when they were actually a "cloth" curtain - albeit now they are over-lapping metal plates - but the result is the same)..

At rest ... the "first" curtain is extended up, blocking the sensor; and the "second" (sometimes called "REAR" curtain) is rolled up, (or the metal plates interleaved), up out of the way. (hidden).

At exposure start, the "first" curtain slides to expose the sensor..

To stop the exposure the "second" (rear) curtain FOLLOWS the first curtain..

NOW ... lets go a step further ....

At a SLOW (long) exposure time, (one that is slower/longer than the max NATIVE flash-sync speed), the first curtain COMPLETELY opens, fully exposing the sensor..

The operative term here is FULLY opened, and FULLY exposing the sensor..

This is important because once the shutter speed exceeds the max native-sync speed (1/125, or 1/250), the first curtain DOES NOT "FULLY" OPEN before the second curtain starts to follow and close. And there is no-time that the sensor is "fully" exposed. The light is basically "painted" across the sensor..

The faster the shutter-speed .... the sooner the second (rear) curtain starts to close .... and the SMALLER THE "SLIT" which is painting the exposure..

Note that the "speed" of the shutter movements is ALWAYS THE SAME ... no matter what the shutter speed. ONLY the "timing" between the first curtain starting to open and the second curtain starting to follow it is different and determines the shutter-speed (exposure time)..

Does the next photo alternatedirection?.

No.

Or does it return to the top after the shutter closes to prepare forthe next exposure?.

Yes..

Actually, I did not read specifically that, per se, but if you lookat explanations about flash sync, it's the only way it makes sense..

Thanks for reading .... JoePhoto.

( Do You Ever STOP to THINK and FORGET to START Again ??? )..

Comment #3

Devnull wrote:.

Buzzphotos wrote:.

I understand that the shutter curtain opens say top to bottom,.

Let's say top to bottom..

Thencloses again from top to bottom..

No, bottom to top..

Doesn't work as you say. If it did, the top would be overexposed and/or the bottom would be underexposed..

Actually, I did not read specifically that, per se, but if you lookat explanations about flash sync, it's the only way it makes sense..

That's not how flash sync works with a focal plane shutter. See here for an explanation:.

Http://en.wikipedia.org/wiki/Focal_plane_shutter.

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #4

I "knew" right, but I wrote wrong..

Writing quickly, the simple ideea "one curtain moves one way opening, than the OTHER curtain closes" came out as one way open, and closing the OTHER way..

The odd part is that I read wrongly other poster's correct answer..

I should read more carefully not only what others write, but what I write..

Apologies to the OP for the confusion..

/d/n..

Comment #5

Just think of it as a 'slot' that varies in width, depending on the shutter speed, that moves across the surface of the CCD..

Cheers..

Comment #6

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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