Image stabilization by jekky
Application in still photography br In photography image stabilization can often permit the use of shutter speeds 24 stops slower exposures 416 times longer although even slower effective speeds have been reported br The rule of thumb to determine the slowest shutter speed possible for hand holding without noticeable blur due to camera shake is to take the reciprocal of the 35mm equivalent focal length of the lens For example at a focal length of 125 mm on a 35mm camera vibration or camera shake would affect sharpness if the shutter speed was slower than 1 125 second As a result of the 34 stops slower shutter speeds allowed by IS an image taken at 1 125 second speed with an ordinary lens could be taken at 1 15 or 1 8 second with an IS equipped lens and produce almost the same quality The sharpness obtainable at a given speed can increase dramatically When calculating the effective focal length it is important to take into account the image format a camera uses For example many digital SLR cameras use an image sensor that is 2 3 5 8 or 1 2 the size of a 35mm film frame This means that the 35 mm frame is 1 5 1 6 or 2 times the size of the digital sensor The latter values are referred to as the crop factor field of view crop factor focal length multiplier or format factor On a 2x crop factor camera for instance a 50mm lens produces the same field of view as a 100mm lens used on a 35mm film camera and can typically be handheld at 1 100 of a second br However image stabilization does not prevent motion blur caused by the movement of the subject or by extreme movements of the camera Image stabilization is only designed for and capable of reducing blur that results from normal minute shaking of a lens due to hand held shooting Some lenses and camera bodies include a secondary panning mode or a more aggressive active mode both described in greater detail below under optical image stabilization br There are two types of implementation lens based or body based stabilization These refer to where the stabilizing system is located Both have their advantages and disadvantages br Techniques of image stabilization br Optical Image Stabilization br An image comparing two close up photographs of a keypad The top image does not have Optical Image Stabilization enabled the bottom image does br An Optical Image Stabilizer often abbreviated as OIS or OS is a mechanism used in a still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor This technology is implemented in the lens itself or by moving the sensor as the final element in the optical path The key element of all optical stablization systems is that they stabilize the image projected on the sensor before the sensor converts the image into digital information br Different companies have different names for the OIS technology for example Image Stabilization IS Canon the first to produce an OIS lens Vibration Reduction VR Nikon Optical SteadyShot Sony Cyber Shot MegaOIS Panasonic and Leica Super Steady Shot SSS Sony Optical Stabilization OS Sigma Vibration Compensation VC Tamron and Shake Reduction SR Pentax br Lens Based Optical Stabilization br In Nikon and Canon s implementation it works by using a floating lens element that is moved orthogonally to the optical axis of the lens using electromagnets Vibration is detected using two piezoelectric angular velocity sensors often called gyroscopic sensors one to detect horizontal movement and the other to detect vertical movement As a result this kind of image stabilizer only corrects for pitch and yaw axis rotations and cannot correct for rotation around the optical axis Some lenses have a secondary mode that counteracts vertical camera shake only This mode is useful when using a panning technique and switching into this mode depends on the lens sometimes it is done by using a switch on the lens or it can be automatic br Some of Nikon s more recent VR enabled lenses offer an Active Mode that is intended to be used when shooting from a moving vehicle such as a car or boat and should correct for larger shakes than the Normal Mode However Active Mode when used under normal shooting conditions can result in poorer results than the Normal Mode br Most manufacturers suggest that the IS feature of a lens be turned off when the lens is mounted on a tripod as it can cause erratic results and is generally unnecessary Many modern image stabilization lenses notably Canon s more recent IS lenses are able to auto detect that they are tripod mounted as a result of extremely low vibration readings and disable IS automatically to prevent this and any consequent image quality reduction The system also draws power from the battery so de activating it when it is not needed will extend the time before a recharge is required br One of the main disadvantages about lens base image stabilization is the expensive price tag that comes with it and not all lenses that Nikon and Canon manufactures are image stabilized Also because the light passing through the lens is being shifted from its true optical path when it projects out the back lens onto the sensor poor Bokeh can result This is the subjective but highly valued by pro photographers quality of the out of focus area around an image In body image stabilization does not have this problem because the light is not being altered only the sensor s position br Sensor shift Optical Image Stabilization br The sensor capturing the image can be moved in such a way as to counteract the motion of the camera a technology often referred to as mechanical image stabilization When the camera rotates causing angular error gyroscopes encode information to the actuator that moves the sensor The sensor is moved to maintain the projection of the image onto the image plane which is a function of the focal length of the lens being used modern cameras can acquire focal length information from the lens Konica Minolta used a technique called anti shake now marketed as SteadyShot in the Sony line and shake reduction SR in the K10D and K100D lines by Pentax which relies on a very precise angular rate sensor to detect camera motion Olympus introduced image stabilization with their E 510 D SLR body employing a system built around their Supersonic Wave Drive Other manufacturers use DSPs to analyze the image on the fly and then move the sensor appropriately Sensor shifting is also used in some cameras by Fujifilm Pentax Samsung Casio Exilim and Ricoh Caplio br The advantage with moving the image sensor instead of the lens is that the image will be stabilized regardless of what lens is being used This allows the stabilization to work with any lens the photographer chooses and reduces the weight and complexity of the lenses The price value is often seen in the ability to buy lower cost quality lenses from makers like Tamron and Sigma and still have stabilized images There are popular lens types that have no in lens stabilization option where sensor based stabilization can be very useful This also allows one to use old manual lenses with this stabilization feature br One of the primary disadvantages of moving the image sensor itself is that the image projected to the viewfinder is not stabilized However this is not an issue on cameras that use an electronic viewfinder EVF since the image projected on that viewfinder is taken from the image sensor itself br Another disadvantage of moving the sensor instead of the lens is that only the main imaging sensor is moved but the autofocus sensor is not moved This means that camera shake can lower the performance of the autofocus system in bad light This is an issue only with DSLRs which have a dedicated phase detection autofocus sensor not an issue with smaller cameras which use the main sensor for contrast detection autofocus br Digital image stabilization br Short video showing image stabilization done purely in software in post processing stage br Real digital image stabilization is used in some video cameras This technique shifts the electronic image from frame to frame of video enough to counteract the motion It uses pixels outside the border of the visible frame to provide a buffer for the motion This technique reduces distracting vibrations from videos or improves still image quality by allowing one to increase the exposure time without blurring the image This technique does not affect the noise level of the image except in the extreme borders when the image is extrapolated br Unfortunately many still camera manufacturers market their cameras as having digital image stabilization when they really only have a mode with a sub optimal image exposure time resulting in pictures with less motion blur but more noise br Stabilization filters br Many non linear editing systems use stabilization filters that can correct a non stabilized image by tracking the movement of pixels in the image and correcting the image by moving the frame The process is similar to digital image stabilization but since there is no larger image to work with the filter either crops the image down to hide the motion of the frame or attempts to recreate the lost image at the edge through extrapolation br Orthogonal Transfer CCD br Used in astronomy an orthogonal transfer CCD OTCCD actually shifts the image within the CCD itself while the image is being captured based on analysis of the apparent motion of bright stars This is a rare example of digital stabilization for still pictures An example of this is in the upcoming gigapixel telescope Pan STARRS being constructed in Hawaii br Stabilizing the camera body br A technique that requires no additional capabilities of any camera bodyens combination consists of stabilizing the entire camera body externally rather than using an internal method This is achieved by attaching a gyroscope to the camera body usually utilizing the camera s built in tripod mount This allows the external gyro to stabilize the camera and is typically employed in photography from a moving vehicle when a lens or camera offering another type of image stabilization is not available br Another technique for stabilizing a video or motion picture camera body is the Steadicam system which isolates the camera from the operator s body using a harness and a camera boom with a counterweight br References br Ken Rockwell Why IS and VR Matter br Image Stabilization Lens vs Body Bobatkins com http www bobatkins com photography digital image_stabilization html Retrieved 2009 12 11 160 br What is Optical Image Stabilizer Technology FAQ Canon Broadcast Equipment br Glossary 160 Optical 160 Image Stabilization Vincent Bockaert Digital Photography Review br Panasonic Mega OIS Explained br Vibration Reduction VR Technology br CameraHobby Nikon AF S VR 70 200mm f2 8 Review br Technical report Canon com http www canon com camera museum tech report 200109 200109 html Retrieved 2009 12 11 160 br http www bokehtests com Site Stabilization_and_Bokeh html br Development of a Test Method for Image Stabilization Systems br Dynax 7D Anti Shake Technology Konica Minolta br Olympus Image Stabilization Technology br dead link br Stop misleading Image Stabilization labels Digital Photography Review Dpreview com 2007 01 05 http www dpreview com news 0701 07010501notimagestabilization asp Retrieved 2009 12 11 160 br The Event Videographer s Resource EventDV net http www eventdv net Articles News Feature Battle of the Software NLEs Part 3 Slow Motion and Image Stabilization 37776 htm Retrieved 2009 12 11 160 br Capabilities Stabilization 2d3 http www 2d3 com capability v 3 Retrieved 2009 12 11 160 br Pan STARRS Orthogonal Transfer CCD Camera Design Gareth Wynn Williams Institute for Astronomy br Multimedia Use Image Stabilization Andy King Web Site Optimization 2004 br Harris Tom How Steadicams Work HowStuffWorks com Discovery Communications LLC http entertainment howstuffworks com steadicam htm Retrieved 2008 07 26 160 br See also br Adaptive optics br Heligimbal br External links br The image stabilizer plugin for ImageJ br Categories Photography equipmentHidden categories All articles with dead external links Articles with dead external links from December 2009
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