Image Stablization

Document Description

This document attempts to detail the advantages and disadvantages of the current set of technologies used to stablize an image prior to it reaching the image recording surface (with respect to its location on said surface) as used in SLR cameras and Image Stablizationlenses. It does not examine the post recording technologies used in many consumer products (such as camcorders or compat digital cameras) which use digital signal processing to improve the image once it's been captured. This document is soley interested in the technologies used to prevent image distortion due to movement in the first place.

For brevity:

• We shall refer to the recording surface as the sensor, this is sensible as most SLRs sold now are of the digital type (i.e. D-SLR) which all use as light collecting sensor of some type. This sensor is most likely to be of the CCD or CMOS type, although in some cases the technologies could be used on be film (we will explain when and when not).

• We shall refer to general camera movement as shake, when we are referring to a specific type of movement we will make this clear.

Whay do we need Stablization

For a number of reasons, the image resulting on the sensor may not remain perfect still over the exposure period, resulting in blurring, i.e. a less than clear image. Under certain frequencies this could be mistaken for poor focus but the image distortion caused by most types of shake are very different (especially mathematically) from focus errors. The blurring visible in the final image is affected by many factors, not just the amount of shaking and we will examine these too, but the main intention is to comparitively examine the stablization technologies used to minimise shake induced blurring.

What is Stablization

Stablization is the process by which the image on the sensor is kept still over the exposure period irrespective of the movement of the camera or lens.

What is Shake

When there is some movement of the camera or lens during the exposure we can say this shake could affect the image. Depending on the type, amplitude and frequency of the shake, and the camera settings used to record the image, the blurring may be more or less visible in the final image.

There are actually a large number of types of movement which can result in image blurring, and to complcate matters these can each occur in a diferent axis.

Roll, pitch, yaw, x,y,z

axis of movement

Shutter speed, aperture setting, focal length of lens.

Summary