LENSES

Image Stabilisation

Find out how image stabilisation in lenses (and cameras) works to keep the image sharp despite camera shake and other involuntary camera movements.
Camera shake is the thief of sharpness. The tremble of your hand as you hold the camera, the slight jarring when you press the shutter release – even a tiny movement during the exposure can result in blurring in the image.

Much of the time, you won't notice the effects of camera shake. If you're shooting with a fast shutter speed or a wide-angle lens, the blurring may not be significant enough for you to register it – but it will still be there, and it might become noticeable if you make a dramatic crop or a large print of the image.

The obvious way to eliminate movement of the camera during the exposure is to fix it to something that will not move, such as a tripod, and to take precautions against jarring it, such as using a remote shutter release. However, a tripod is effective only if it is sturdy, which usually means heavy, so you can't always carry one with you. There are also many situations where a tripod is just not practical, and several where the use of a tripod is not permitted.

Fortunately, Canon offers another method of reducing, if not eliminating, the effects of camera shake: Image Stabilisation (IS).

The first lens with Image Stabilisation was introduced in 1995. It approached the problem of camera shake laterally. Rather than trying to stop the camera moving, a stabilised lens introduces a compensating movement within it, with the aim of keeping the image static on the camera's sensor.
Canon EF 400mm f/2.8L IS III USM lens.

The Canon EF 400mm f/2.8L IS III USM, one of the range of Canon lenses with built-in optical Image Stabilisation. Note the switch on the side for selecting between the three IS modes available.

Cutaway drawing of a Canon EF 400mm f/2.8L IS III USM lens showing the lens elements.

The IS unit is just one of the complex optical and electronic elements in a Canon lens.

How Image Stabilisation works

Image Stabilisation was available for camcorders long before it was introduced in EF lenses. Even when both electronic and optical systems were available, size or weight constraints meant that neither was suitable for EOS cameras. So Canon went back to the drawing board and took a fresh look at the problem.

Canon's solution was to use a group of elements inside the lens that move perpendicularly to the lens axis to counteract camera shake. The movement of this special lens group is controlled by an on-board processor, and crucially, there is no reduction in the optical performance of the lens.

With a stabilised lens, camera shake is detected by two gyro sensors inside the barrel, one for yaw (side-to-side movement) and one for pitch (up-and-down movement). The sensors detect both the angle and speed of the movement.

The following sequence of events takes place when the camera shutter release button is partially depressed:

• The special stabilisation lens element group, which is locked in a central position when not active, is released.
• Two gyro sensors start up and detect the speed and angle of any camera/lens movement.
• The gyro data is passed to a microprocessor in the lens, which analyses it and formulates an instruction for the special stabilisation lens element group.
• This instruction is transmitted to the stabilisation lens element group, which then moves at the appropriate speed and direction to counteract the camera movement.
• This complete sequence is repeated continuously, so that there is an instant reaction to any change in the amount or direction of the camera shake.

Image Stabilisation is effective with movement across a range of frequencies, so it can cope not only with simple camera shake (0.5Hz to 3Hz), but also with the engine vibrations encountered when shooting from a moving vehicle or helicopter (10Hz to 20Hz).

When the first EF lens with IS was introduced, it was the first time that a high speed 16-bit microprocessor had been incorporated in a lens. The processor simultaneously controlled the Image Stabilizer, Ultra Sonic Motor (for focusing the lens) and the electromagnetic diaphragm (for setting the lens aperture).

The power required by the image stabilisation system in a lens comes from the camera battery. This means that the battery life is slightly reduced when an IS lens is mounted on the camera and IS is switched on.
Diagram of the path of a ray of light through a lens and the effect of movement on the resulting image.

When the camera is static, the rays of light pass through the lens and form an image on the sensor. When the camera moves, the rays of light from the subject are bent relative to the optical axis and the image shifts slightly on the sensor. You can see this effect in the camera viewfinder if you gently shake the camera while viewing a subject.

The Image Stabilizer unit from a Canon lens.

The tech behind Canon's Image Stabilizer system includes gyro sensors to detect the speed and direction of movement, special "floating" lens elements that can move in order to compensate for this movement, and a microprocessor to control the whole operation.

Diagram of the path of a ray of light through a lens, corrected for movement and thus steadying the resulting image.

In an IS lens, gyro sensors detect the camera movement, and the microprocessor in the lens moves the IS lens elements the precise amount and direction required to counteract the amount and direction of the camera shake. The result is that the image remains stationary on the camera sensor.

Diagram of the various planes of movement that a camera and lens might suffer.

The camera and lens might move in a number of ways. Up-and-down rotational movement is called pitch; side-to-side rotational movement is termed yaw. Rotation around the lens axis is roll; lateral and vertical movement (in the X and Y axes respectively) are also possible. Advanced modern IS systems can detect and attempt to correct for all these five kinds of movement.

Image Stabilizer modes

One problem with the first EF lenses with IS was that the system saw a panning movement as camera shake and tried to overcome it. This caused the viewfinder image to jump about, making it difficult to see and frame the subject accurately.

On more recent IS lenses, you have the option of two or three IS modes, as follows:

Mode 1: When IS Mode 1 is selected on a stabilised lens, the IS system works in the same way as the original system and will correct both pitch and yaw movements. It is the best mode to use when you're photographing static subjects.

Mode 2: Mode 2 is the best setting to use when you're panning the camera to follow a moving subject. It sets the lens to ignore the panning movement and compensate only for movement that is perpendicular to the panning direction. It also ensures a smoother image in the viewfinder.

The IS system automatically detects the direction of the pan, so there's no need to worry about whether you are composing portrait-format or landscape-format images or which direction you are moving the camera.

Mode 3: Image Stabilizer Mode 3 was introduced in 2010 with the EF 300mm f/2.8L IS II USM and EF 400mm f/2.8L IS II USM (now succeeded by the EF 400mm f/2.8L IS III USM) lenses. It's also on the EF 400mm f/4 DO II IS USM, EF 500mm f/4L IS II USM, EF 600mm f/4L IS II USM (now succeeded by the EF 600mm f/4L IS III USM) telephoto lenses, EF 100-400mm f/4.5-5.6L IS II USM, EF 200-400mm f/4L IS USM Extender 1.4x and RF 70-200mm F2.8L IS USM.

This useful mode takes the benefits of standard IS (effective for both horizontal and vertical camera motion) but, instead of it being active all the time, it activates only when you fully press the shutter button to capture an image.

Mode 3 is especially useful for sports photography where you are likely to be moving between subjects quickly. In IS Mode 1 this can create a bump or jump within the viewfinder as the IS races to keep up with the lens movements. Instead, by not activating until the shutter button is fully pressed, it saves the system trying to compensate for random, rapid lens motion and compensates only at the point you are taking an image.

Also, by limiting the activation to the point of capture, it ensures that the stabilisation group is centred within the barrel, therefore offering the maximum degree of stabilisation.

Hybrid IS

Introduced with the EF 100mm f/2.8L Macro IS USM lens in 2009, Hybrid IS takes the image stabilisation concept and applies it to macro photography. When you're using longer lenses or in general purpose shooting, camera shake appears to be rotational – that is, an up-and-down (pitch) or side-to-side (yaw) movement around a point, that point being the camera. This is effectively corrected by the IS motors contained in the lenses. However, when you move in close for macro photography, the camera shake motion appears to be less rotational and more shift based – as if the whole frame is shifting up-and-down or side-to-side parallel to the subject. This is what Shift IS, found in the Hybrid IS system, aims to correct.
 A shot of a go-kart race with the background blurred by the camera panning.

When panning the camera to follow a moving subject, select IS Mode 2. In this mode the IS will ignore camera movement in the direction of panning and compensate only for any movement perpendicular to this.

Diagram of pitch and yaw movement compared to side-to-side camera shake.

In macro photography, the camera tends to suffer not only pitch and yaw movements (top image) but also side-to-side movements in the X and Y axes (bottom image). Hybrid IS is designed to address this particular set of problems.

How effective is Image Stabilisation?

The earliest IS lenses enabled sharp images to be captured at shutter speeds about two stops slower than normal. This means, for example, if you can obtain a sharp image shooting handheld without Image Stabilisation at a shutter speed of 1/60 sec, then you will produce results of similar sharpness at 1/15 sec with Image Stabilisation, other factors staying the same.

One of these factors – a key one to consider – is the lens focal length. Increasing the focal length not only magnifies the subject, it also magnifies the effects of camera shake. A useful rule of thumb is that, without IS, you should use a shutter speed at least equal to the reciprocal of the focal length when holding the camera and lens by hand. So if you're shooting handheld without IS and the focal length of the lens is 500mm, then the shutter speed should be at least 1/500 sec. If the lens you're using offers 2 stops of IS, then you can expect to be able to use a shutter speed of 1/125 sec instead (that is, 2 stops slower than 1/500 sec) and still get a sharp shot. More recent IS lenses have improved their effectiveness, giving a 4-stop or a 5-stop gain. A 4-stop gain means that instead of 1/500 sec you should be able to go to 1/30 sec, while 5-stops will take you to 1/15 sec. Or to put it the other way around, a 5-stop gain means that shooting with a shutter speed of 1/15 sec with Image Stabilisation gives the same image sharpness as shooting at 1/500 sec without Image Stabilisation.

Keep in mind that Image Stabilisation only reduces the effect of camera shake − it has no effect on blurring caused by subject movement.
Diagram of the Dual Sensing IS system in a Canon EOS R.

The Canon EOS R uses information from both the camera and the lens to correct blur. The IS system acquires both camera-shake data from a gyro sensor in the lens and image data from the camera's CMOS sensor. This Dual Sensing IS system can accurately detect and compensate for low-frequency (slow) blur that used to be hard to detect with gyroscopic sensors alone.

Camera compatibility

The optical Image Stabilisation system we've been talking about – gyros, microprocessor and special lens element group – is part of the lens, not the camera. This means that the IS can be optimised for each specific lens, and that the IS will work regardless of which camera you use the lens with. In some circumstances you might see the image move in the viewfinder after exposure, but this will not affect the sharpness of the exposed image. If you're using the built-in flash in some early EOS film cameras, you may see the viewfinder image shake while the flash is recycling as power is temporarily diverted from the IS to charge the flash, but this will not affect the sharpness of the exposed image.

Note that Image Stabilisation does not operate with most EOS cameras if you're using Bulb mode for long exposures. IS is likely to be ineffective for long exposures in any case, and you'll get better results switching off IS and ensuring the camera is secured against any movement.

In this article we have only been speaking about the optical IS found in lenses, but the Canon EOS R5 and EOS R6, released in 2020, have introduced 5-axis in-body Image Stabilisation (IBIS) for the first time in Canon cameras. This operates in tandem with the IS in lenses and is particularly effective against low-frequency vibration (such as that caused by your breathing and heartbeat) and at wider focal lengths, while optical in-lens IS is especially effective at telephoto focal lengths. The in-body and in-lens IS systems working together can deliver a groundbreaking 8-stops of combined IS. With some lenses with a large image circle, such as the RF 28-70mm F2L USM and RF 85mm F1.2L USM, the camera's in-body image stabilisation can deliver up to 8-stops of IS even though the lenses do not have built-in optical stabilisation.

In practical terms, following the examples we used above, 8-stops of IS means you can shoot handheld with a 500mm lens at 1/2 sec, and in fact with a wide-angle lens you could shoot handheld with a 4-second exposure. That’s long enough to blur moving water but still keep the landscape sharp without the need for a tripod.

Find out more about in-body Image Stabilisation in the EOS R5 and R6.
Diagram of the combination IS system in a Canon EOS R5.

In the Canon EOS R5 and EOS R6, the in-body Image Stabilisation system (IBIS) works in tandem with optical IS in the lens to deliver unprecedented levels of stabilisation. The lens microprocessor receives data from the gyro sensor in the lens, while the DIGIC X processor in the camera receives data from a gyro sensor and an acceleration sensor in the camera. The two processors share information in real time in order to adjust both the lens elements and the camera sensor to produce a super-steady image.

The Image Stabilisation unit from a Canon EOS R5.

Much as the IS system in a Canon lens uses special movable lens elements, the in-body Image Stabilisation tech in the Canon EOS R5 has the imaging sensor "floating" magnetically so that it can move to compensate for camera movement.

Accessories for IS lenses

IS lenses work well when used with accessories. For example, they are very useful when you add a lens extender to increase the effective focal length of the lens by 1.4x or 2x. As already mentioned, increasing the focal length means that the effects of camera shake are magnified, so the IS is extremely beneficial.

Canon EF extenders are compatible with L-series and DO lenses of focal length 135mm and greater, and a small number of wide-aperture telephoto zoom lenses. Canon RF extenders are compatible with RF lenses above 300mm. Both are also compatible with many IS lenses.

Image Stabilisation also remains effective when extension tubes or close-up lenses are used.

Keep a tripod

Although an IS lens gives more opportunities for handheld shots, there will still be times when the support of a tripod is needed − with exposure times of several seconds, for example, or when you're working with heavy lenses.

With some of the earlier lenses, you needed to switch the IS off when using a tripod as the lack of movement confused the system and the image started to jump around the viewfinder. However, even when using a tripod, there can be some camera movement in high wind or with super telephoto lenses, which means the IS system can be invaluable. More recent IS lenses are able to detect the use of a tripod and automatically disable the IS, if necessary.

You should also leave the Image Stabilisation on when using a monopod, as it is unlikely you will be able to keep this type of support perfectly still.

Kirjoittaja Angela Nicholson


Related articles

Get the newsletter

Click here to get inspiring stories and exciting news from Canon Europe Pro