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Sony XDCAM EX Pro Handhelds
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Old December 4th, 2007, 11:06 AM   #1
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What the heck is a rolling shutter?

Read other threads talking about it, but none of them go into to detail as to what it is...

How does the shutter on the EX-1 compare a camera like the JVC 100? Specifically, can you get SAVING PRIVATE RYAN -type look with this camera?

Thank a lot....

john

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Old December 4th, 2007, 11:24 AM   #2
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do a google search for CMOS "Barry Green". Check out that article. :)

Carl
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Old December 4th, 2007, 11:35 AM   #3
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Don't take this the wrong way, because Barry Green's forgtten more about cameras than I will ever know, but he may be a little "close" to the problem. Know what I mean?

Also, I'd just as soon stay here - it's easier on the eyes if nothing else!

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Old December 4th, 2007, 11:38 AM   #4
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Well, that article is incredibly good. I found it based on CH those search instructions elsewhere. Even if you take it with a grain of salt, it includes all of the technical information to back up it's claims, and videos to demonstrate.

Close to the problem or not, it's a good article, and worth the read! No use asking people to type out information that's readily available, even if you don't like the color scheme of the website it's on. :D

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Old December 4th, 2007, 12:50 PM   #5
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Well the article says little other than, from what I could get out of it, that a rolling shutter scans vertically, top to bottom (at least that's what the video illustrations shows) and it does so in sections, whereas CCD/Global doesn't, instead viewing one frame as a whole.

Found it to be more of a warning not to use cameras that use the system - and perhaps with good reason - it does seem strange not to try and emulate a film camera as close as possible.

But there must be some reason to use this method, some postive benefit. And that is not discussed. I assume that any scaning (versus whole frame grab) is done incredably fast. What I'm not sure about is how many "segments" of the frame it must scan to get the entire image - say, 2 versus some much higher number.

SOOOO.... if I buy a EX1, can I still do the RYAN-type stutter?

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Old December 4th, 2007, 01:54 PM   #6
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Many film cameras have something approximating a rolling shutter.

The Mitchell GC (and derivatives thereof), which was a staple in Hollywood from the 20s to the 90s, has a rotating shutter at the focal plane. Each exposure is a radial wipe across that frame by the shutter.

Many other film cameras are similarly designed. Most of Panavision's gear until very recently was based on the Mitchell movement.

At wider shutter angles, the wipe is not significant compared to the moment when the entire frame is open to exposure, but at smaller shutter angles (the Mitchell could go down to 10° if I remember correctly) the exposure was essentially a slit scan across the frame and could create the same type of distortions as a rolling shutter.

The "global shutter" ideal is for video only - film has always had a "rolling shutter" to some extent.

Also, 35mm SLR still cameras at high shutter speeds exhibit the same sort of distortion, because, in many cases the shutter is a slit that scans across the frame horizontally. More recent cameras have sped the movement of the shutter up and made the shutter vertical to reduce the distortion and to allow flash sync at higher shutter speeds - an issue analogous to the "partial exposure" of the rolling shutter camera.
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Old December 4th, 2007, 02:05 PM   #7
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Quote:
Originally Posted by Eric Pascarelli View Post
Many film cameras have something approximating a rolling shutter.

The Mitchell GC (and derivatives thereof), which has was a staple in Hollywood from the 20s to the 90s, has a rotating shutter at the focal plane. Each exposure is a radial wipe across that frame by the shutter.

Many other film cameras are similarly designed. Most of Panavision's gear until very recently was based on the Mitchell movement.

At wider shutter angles, the wipe is not significant compared to the moment when the entire frame is open to exposure, but at smaller shutter angles (the Mitchell could go down to 10 if I remember correctly) the exposure was essentially a slit scan across the frame and could create the same type of distortions as a rolling shutter.

The "global shutter" ideal is for video only - film has always had a "rolling shutter" to some extent.

Also, 35mm SLR still cameras at high shutter speeds exhibit the same sort of distortion, because, in many cases the shutter is a slit that scans across the frame horizontally. More recent cameras have sped the movement of the shutter up and made the shutter vertical to reduce the distortion and to allow flash sync at higher shutter speeds - an issue analogous to the "partial exposure" of the rolling shutter camera.
Good points Eric. I had never thought to look at it from the mechanical shutter point of view. BTW, I learned after shooting the first roll of film in my trusty old Canon AE-1 that when the flash sync says 1/60 only, they really mean it (got some of those partial exposed pictures back from the lab).

Although that article may have a lot of technical merit, the timing and location of its release don't help with the credibility factor.

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Old December 5th, 2007, 05:29 AM   #8
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Well, I mean, that's the point, isn't it?

Not so much that what's said isn't accurate, bu that it just doesn't give the whole picture....

How would a film camera have what is discribed in the article at all? Would a rolling shutter on a Mitchel film camera "sample" a single frame 2 or 3 times in diferent sections (which is apparently how a rolling shutter works), or I am I totally wrong about this?

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