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Old Dec 29, 2009, 2:07 PM   #1
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Default Global Shutter CMOS

It seems there are CMOS devices being produced now that have Global shutters:

http://www.dalsa.com/mv/products/cam...spx?fam=Falcon

I wonder when this will eventually filter down to consumer level products.
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Old Dec 29, 2009, 6:18 PM   #2
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the best explanation about this is the graphic they provide on their site. excellent

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Old Dec 29, 2009, 7:04 PM   #3
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motion blur must have been the OLD rolling shutter

Rolling shutter looks like it dragging its rear

And Global looks like its pusing foward

I wonder if ow you look at it filming from one particular side you'll call it global, when its Rolling. and rolling wen its global

is rolling and global anywhere the same.

or is global the bottm is being pushed, and rolling the top is being pushed
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Old Dec 29, 2009, 7:24 PM   #4
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Global shutter simply means the entire frame is captured at once, just like taking a film photo.

The way CMOS sensors traditionally have worked is rolling shutter, which means the image is scanned pixel by pixel, line by line. If both the camera and the object being photographed or video-recorded are perfectly still, this works fine. But if either the camera or the object is moved around during this scanning process, the result is a distorted shape on the image.

Also, the slower that the CMOS sensor scans each frame, the worse the rolling shutter distortion gets. That's why 60 fps almost always looks better for moving objects on a CMOS camcorder than 30 fps, because there is less time for objects to move around in the shorter time it takes to scan each frame. (If you want to see really bad rolling shutter, the Vivitar 810HD records 1280x720 "HD" video using a CMOS sensor at a whopping 20 fps!)
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Old Dec 29, 2009, 7:47 PM   #5
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id expect it on the high end sony and canons before ever seeing it on a aiptek or sorts
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Old Dec 29, 2009, 8:36 PM   #6
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I agree with you. Simple and to the point.

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the best explanation about this is the graphic they provide on their site. excellent

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Old Dec 29, 2009, 8:41 PM   #7
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id expect it on the high end sony and canons before ever seeing it on a aiptek or sorts
Of course! That's how it always works, as technology becomes cheaper to implement it trickles down. Considering none of the current consumer cams have a global shutter, this would obviously be an improvement even if only for high end devices initially.

We forget how far we have come. Although CMOS sensors have been around as long as CCD's, it wasn't that long ago that they were not that good even in daylight. Now CMOS sensors as as good if not better than CCD in some cases as long as there is sufficient light. Once global shutter becomes cheap enough to implement it will be the icing on the cake.
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Old Dec 29, 2009, 11:01 PM   #8
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Of course! That's how it always works, as technology becomes cheaper to implement it trickles down. Considering none of the current consumer cams have a global shutter, this would obviously be an improvement even if only for high end devices initially.

We forget how far we have come. Although CMOS sensors have been around as long as CCD's, it wasn't that long ago that they were not that good even in daylight. Now CMOS sensors as as good if not better than CCD in some cases as long as there is sufficient light. Once global shutter becomes cheap enough to implement it will be the icing on the cake.
Maybe I'm just too sensitive, but I see rolling shutter even on $1200 Sony HD camcorders. At that price I'd want my video quality to be darn near perfect! So hopefully these high-end HD camcorders will adopt global shutter image sensors soon.

And remember, it took a while for even CCDs to become accepted. Many TV studios were still using vacuum tube image sensor cameras until the late '80s and early '90s because it took that long for CCDs to catch up to tube sensors in terms of low light sensitivity, color rendition, and resolution. At that time, the only real flaw that tube cameras had (besides high maintenance costs) was a distinctive "comet tailing" or "streaking" of bright lights and reflections.
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Old Dec 30, 2009, 4:26 PM   #9
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Maybe I'm just too sensitive, but I see rolling shutter even on $1200 Sony HD camcorders. At that price I'd want my video quality to be darn near perfect! So hopefully these high-end HD camcorders will adopt global shutter image sensors soon.

And remember, it took a while for even CCDs to become accepted. Many TV studios were still using vacuum tube image sensor cameras until the late '80s and early '90s because it took that long for CCDs to catch up to tube sensors in terms of low light sensitivity, color rendition, and resolution. At that time, the only real flaw that tube cameras had (besides high maintenance costs) was a distinctive "comet tailing" or "streaking" of bright lights and reflections.
Yet CCD's are now prized by astronomers for astrophotography because of their much better low light sensitivity compared with film!

Due to the design of CMOS, I have read that adding a global shutter is certainly not straightforward but I would be very curious as to how much extra cost implementing a global shutter on a CMOS chip really is.

It seems there isn't a current CMOS camcorder, even a professional one, that doesn't have rolling shutter. Even the Red One Camcorders use rolling shutter CMOS chips. Considering their cost, it makes me wonder if there is some kind of disadvantage to implementing a global shutter on CMOS or it really is so difficult to implement that the cost is prohibitive even for most professional devices.
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Old Dec 30, 2009, 4:55 PM   #10
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Yes, just like rgvcam points out, even higher end cameras have to deal with rolling shutter.

It is important to note that there is nothing wrong with these cameras. The higher price has to do with a bigger sensor, better optics, higher quality build, a wide array of manual controls, and probably paying for the name brand.

The rolling shutter effect is there simply because regardless of the size of the sensor, the way images are captured is the same: scanning from top to bottom (or sometimes bottom to top) and not capturing the whole frame at once (like on CCD sensors).

In fact, I was able to save a video where high-end software developers also devise solutions to deal with the rolling shutter effect. The software developer being "The Foundry" (makers of a very high-end compositing software called "Nuke" and several plugins for after effects, FCP, avid, combustion, fusion and shake) offer a software-based solution (rendering, and re-encoding necessary of course.. also time consuming).

I saved this video back when they were developing the plugin:
http://vimeo.com/4553162

And this is one of their new plugins for after effects:
http://www.youtube.com/watch?v=Zt0u9hsPuZY

So yes, even expensive cameras (Canon EOS 7D, Canon 5DmkII, RED One) have rolling shutter.
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