A quick look at image stabilisation

Image Stabilisation

Image Stabilisation

Image stabilisation helps you get a sharper picture.

Good images rely on a steady hand or a tripod. You also get a help from the image stabilisation in your camera or lens. These systems help your lens stay steady. Here we are going to get a look at what is involved and how to use it.

What is image stabilisation?

The term “Image stabilisation” represents a number of technologies used to reduce blurring caused by camera movement during exposure. It compensates for movement in two planes. These are referred to as pan (lateral twisting or yawing movement) and tilt (vertical or pitching movement).

Camera movement is recorded as blur when the shutter is open long enough for the movement to be captured. The slower the shutter speed the more likely it is that the movement will be detected. The tiny, but continuous movements of our hands tend to make hand held shots a little soft. Longer exposures will be even softer since the tiny movements will continue blurring the shot throughout the exposure.

Using an image stabilisation technology allows a mechanism to off-set or compensate for the movement not prevent it. Extreme or large movements will still cause blur during the exposure. However, image stabilisation systems are designed to compensate for the movements created by the almost imperceptible movements of our hands while hand-holding a shot. Typically recent image stabilisation systems will compensate for exposures four to sixteen times longer than could be hand held without the compensation. This would mean that instead of using a shutter speed of 1/250th of a second, you can use image stabilisation to get a shutter speed of around a 1/30th of a second and still get similar image quality. This could significantly improve the light levels in your exposure.

Types of image stabilisation

Optical image stabilisation: This type is mounted in the lens. It uses high speed motors to shift a lens element around changing its orientation to compensate for the movement of the camera. It is highly accurate, compact and fast. It does add quite a lot of weight (and expense) to the photographic lens unit overall. However, it performs really well under all types of movement even fairly extreme movement that might be found in panning for example. It will not prevent the gross movement blur, but will compensate for the tiny variations while panning for example.

In-camera stabilisation or sensor shift stabilisation
This technology uses motor technology to move the Digital Image Sensor to compensate for the movement of the camera. This method concentrates the stabilisation in the camera body and therefore it is only paid for once on the purchase of the camera body (unlike lens-based systems). Sensor shift technology tends to mean the lens is lighter too making handling easier for some people. This type of system does not cope as well as lens-based systems for more extreme movements. Long focal lengths and telephoto lenses will tend to exaggerate the degree of movement of a beam of light hitting the sensor. Consequently the sensor needs to be able to compensate for more extreme vibrations or movements to get the same image quality as a lens system. As the sensor shift system is limited by its range of movement it has limited tolerance at the more extreme end of the range.

Stay sharp!

Many learners find that the softness they get when using a DSLR is very frustrating. While image stabilisation helps, it does not cure the problem. Remember that these systems can only compensate, not prevent, movement blur and softness. So you need to take other steps to make your shots sharp. Here are some issues to consider regarding image stabilisation…

High ISO (in manual control modes): Raising your ISO can help reduce movement blur because you are making the sensor more sensitive to light. Your image sensor will be exposed more readily allowing you to still have a faster shutter speed to take your shot – then movements don’t have time to make the shot soft. Remember, high ISO may increase your digital noise, particularly with very high ISO levels (say 800 or more).

One way to overcome this softness created by hand movement is to raise the and set a faster shutter speed The point and shoot mode or auto mode of your camera will do this to ensure your get sharp shots in most daylight situations. Of course this means a short exposure which may not be suitable for your shot.

Wide aperture(in manual control modes): This too will allow more light into the shot and will allow you to have a faster shutter speed. However, the depth of field will be reduced and that will reduce your sharpness in some areas of the shot.

Use a tripod: Using a tripod is probably the best way to get a sharp shot. In most situations you should turn off your image stabilisation to use a tripod. The motors that do the stabilisation actually create vibration in the tripod and can cause softness. Some systems compensate automatically for being on a tripod so read your technical manual to get guidance for your camera.

Panning: This will definitely create movement blur. But some image stabilisation systems have mechanisms to reduce the vertical movement while panning. In this case make sure you know how to switch to this mode. The difference it can make to getting a moving object sharp is surprising.

Mirror lock-up: Vibration is caused when the reflex mirror in a DSLR flips up. You can lock up these mirrors while you take the shot. The procedure for that is different on every camera so check the manual for the correct method. The image stabilisation mechanisms will not compensate for movement caused by the mirror movement.

Careful use of the shutter button
Don’t stab the shutter button. Roll your finger onto the button gently depressing it. If you stab at it there will almost certainly be an erratic movement that the image stabilisation will not be able to compensate for.

Eagerness!
While enthusiasm is great, taking the camera away from your face too quickly can induce movement before the exposure is complete. Image stabilisation will not compensate for this type of action. Try to count to two before taking the camera away from your face.

Improving overall

Image stabilisation systems vary in their effectiveness according to model, camera, lens, use and how much movement there is. They can be very effective in helping you gain control over your sharpness but they are not the final answer. Sharpness involves a range of techniques and procedures which you will need to learn and practice to improve. Nevertheless, if you are hand-holding a shot you will get significant improvements in sharpness by using these systems. If you want to know a little bit more detail about image stabilisation you can see some more detail in Definition: Image stabiliser; Image stabilisation.

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.
See also: Editors ‘Bio’.
By Damon Guy see his profile on Google+.

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