Rolling shutter 1

Rolling shutter

Distorted rotor blades due to the rolling shuttereffect

Moving car taken with CMOS camera phoneexhibits Skew.

A photo exhibiting Partial Exposure. Lightingconditions changed between the exposure of the

top and bottom parts of the photo.

Rolling shutter (also known as line scan) is a method of imageacquisition in which each frame is recorded not from a snapshot of asingle point in time, but rather by scanning across the frame eithervertically or horizontally. In other words, not all parts of the image arerecorded at exactly the same time, even though the whole frame isdisplayed at the same time during playback. This produces predictabledistortions of fast moving objects or when the sensor captures rapidflashes of light.

This method is implemented by rolling (moving) the shutter across theexposable image area instead of exposing the image area all at thesame time (the shutter could be either mechanical or electronic). Theadvantage of this method is that the image sensor can continue togather photons during the acquisition process, thus increasingsensitivity. It is found on some film cameras (such as the GraflexSpeed Graphic), as well as digital still and video cameras using CMOSsensors, and is most noticeable when imaging extreme conditions ofmotion or the fast flashing of light. While some CMOS sensors use aglobal shutter,[1] the majority found in the consumer market utilize arolling shutter.

Rolling shutters can cause such effects as:• Skew. The image bends diagonally in one direction or another as

the camera or subject moves from one side to another, exposingdifferent parts of the image at different times.

• Wobble. This phenomenon is most common in hand-held shots attelephoto settings, and most extreme in cases when the camera isvibrating due to being attached to a moving vehicle. The rollingshutter causes the image to wobble unnaturally and bizarrely. Thisis often called the jello effect.

• Partial Exposure. If a camera flash goes off in the shot, the quicknature of the flash may only be present for some of the rows ofpixels in a given frame. So as an example, the top 1/3 of the picturemay be brightly lit by a flash, while the bottom 2/3 of the picture isdark and unlit as the time it took for the flash to occur was onlysequenced in a short amount of time as the CMOS imagersequences a frame. The difference between the two distinct parts ofthe frame can look odd. Similar problems can arise with emergency vehicle lights, some fluorescent lighting, orany extreme situation where very fast motion or very fast bursts of light are seen in the time between when theCMOS chip sequentially records a frame.

• Spatial and temporal aliasing.CCDs (Charge-Coupled Devices) are alternatives to CMOS sensors. CCDs use what is referred to as global shutterswhich take a single snapshot representing a point of time and do not suffer from these motion artifacts.[2]

Rolling shutter 2

Notes[1] "Image Sensors - MT9M413C36STC - Aptina Imaging" (http:/ / www. aptina. com/ products/ image_sensors/ mt9m413c36stc/ #overview).

Aptina.com. 2008-03-03. . Retrieved 2010-08-21.[2] "To CCD or to CMOS, That is the Question | B&H Photo Video Pro Audio" (http:/ / www. bhphotovideo. com/ find/ newsLetter/

Comparing-Image-Sensors. jsp). Bhphotovideo.com. . Retrieved 2010-08-21.

External links• An example of rolling shutter effects (http:/ / www. youtube. com/ watch?v=LVwmtwZLG88)

Article Sources and Contributors 3

Article Sources and ContributorsRolling shutter  Source: http://en.wikipedia.org/w/index.php?oldid=383317066  Contributors: Algocu, Aqwis, Armadillo7777, Athiril, Ctrlfreak13, EastTN, Fabrictramp, Friday13, Gidovski,Jakerno, Janke, Japerry007, McGeddon, Mikus, Quantumor, RainerBlome, Walterny, Xingbo, 21 anonymous edits

Image Sources, Licenses and ContributorsFile:Focalplane shutter distortions.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Focalplane_shutter_distortions.jpg  License: Apache  Contributors:http://chdk.wikia.com/wiki/User:KeoeeitFile:CMOS rolling shutter distortion.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:CMOS_rolling_shutter_distortion.jpg  License: GNU Free Documentation License Contributors: User:Axel1963File:Lightning_rolling_shutter.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lightning_rolling_shutter.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:Kalleboo

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