Wednesday, 14 April 2010

Image Stabilisation – in lens or in camera – is it worth it?

Image stabilisation (IS) is not a new technology, however due to marketing a lot of confusion has been generated to the benefits of IS in both lenses and those digital cameras which feature IS in-camera.
To firstly understand what IS does and why you may need a lens/camera with the IS feature it is important to understand what actually causes blurred images.

  1. Camera Shake
    Camera shake is caused by pressing the shutter release button and moving the camera during the exposure. Every time we press the shutter we cause some amount of movement. This may be ever so slight and depending on how steady you are, blurriness can go unnoticed.

    There are other factors that contribute to each person’s level of ‘steadiness’ such as age, medication, sleep deprivation, sugar levels etc. Even if you have ‘sniper-steady’ hands there are shutter speeds you will not be able to hand hold without causing blur.

    The likelihood of camera shake increases as the focal length used increases. As focal length increases, the slight movement of the camera get magnified and therefore the chance of blurred images increases. (See previous blog ‘Reciprocal of Focal Length Rule of Thumb’.
  2. Subject Movement
    Caused when your subject moves during the exposure, that is: while the shutter is open and the camera is recording the scene.

Also called Anti-Shake, Vibration Reduction, IS may be optical (in lens) or image sensor based (in-camera) and counters the effect of camera shake ONLY. It makes no difference to your exposure settings. The technology, and in jumps the physics of photography, ‘moves either a lens element (optical image stabilization or O.I.S. or simply IS) or the image sensor (CCD Shift) to compensate for camera shake. In doing so, it eliminates, or reduces the likelihood of obtaining blurred images due to camera shake. It helps to ‘steady’ the image projected back in camera by the use of a ‘floating’ optical element. Canon IS stabilised lenses have as a IS suffix after their name, Nikon uses the VR "Vibration Reduction" suffix on their image stabilised Nikkor lenses.
So let’s return to the original question: Image Stabilisation – in lens or in camera – is it worth it?
Once again there are positives and negatives to both options and even to having IS at all. It basically gets down to the environment you are shooting in and your subject.
One could try and argue that all you have to do to counter balance low shutter speeds and camera shake is to increase the ISO, however in all but the higher end professional bodies shooting at high ISO ratings produces noise. Fine if all you wish to produce is 6”x4” prints or web based images but high ISO also produces a decrease in image quality. Even for the keen enthusiast this combination quickly becomes unacceptable.
Take this example: You are using a 60mm lens, the reciprocal of focal length rule of thumb says we need to use a shutter speed of 1/60th or faster to eliminate camera shake. But the light is low, you don’t want to increase your ISO for the reasons outlined above and you are either using your maximum aperture or require a certain depth of field at the aperture you have chosen, and you need to use a slower shutter speed such as 1/15th to gain a correctly exposed image. If a tripod is not an option then you cannot hand hold the camera without there being blur from camera shake. Using IS allows us to take our exposure 2-3 stops below that required so now with this scenario we are able to hand hold without worrying about camera shake. If the light drops another 2 stops and say we require a shutter speed of ¼ the IS will not eliminate it totally but it will reduce it.
There are a few situations this becomes advantageous:
Adventure Traveller/Photographer:  No one can argue - 2 stops from IS is 2 stops worth of advantage and carrying a tripod, no matter how light they are now being produced, can be cumbersome especially if you are trekking, kayaking, biking etc.
Those that need to use long focal length lenses: Such as nature, wildlife and sports photographers who need to use long focal length lenses and hand hold these 2 stops are invaluable.
In-low situations where the subject may be moving: and this includes breathing where you either don’t want to use flash or flash is not an option. This is particularly of assistance to portrait and wedding photographers.
Image stabilised lenses and cameras are heavier. Yes, some may be only 100 grams but when carrying all your gear e very gram adds up in the pack or on the back.
IS also means a new set of components or moving parts. This is now another thing that can breakdown and need repair. If it’s the lens that contains IS then the lens needs to be sent away, if it’s the camera then you need to be aware you may lose the body for 1-2 weeks (or more).  If I had the choice I know which one I would prefer to be without.
It is also reported IS lenses do not last as long although there is no concrete evidence we can find on this. For most photographers lenses are a longer-term investment than camera bodies – they will spend more money on good glass. If IS lenses do in fact have a shorter life span I feel many will not notice it due to the time between the purchase  and the ‘breakdown’.
IS lenses are more expensive than those that don’t have it. There has to be something added on for R&D. If you are a landscape photographer who uses a tripod it is useless, in fact you need to have it turned off! If you are shooting outdoors in bright sunny conditions or in a studio under controlled lighting it also would be of little benefit as the shutter speed being used would be appropriate for the focal length of the lens being used.
With in-camera IS, users have the advantage of having IS available with almost any lens they wish to use – sometimes a big bonus.
In fact, we could say in some cases IS is almost a virtual tripod.
Both in-camera and lens IS have their advantages and disadvantages. For general interest shooters there is an obvious benefit with in-body IS. Individually we all have to make an informed judgement for ourselves. Will the leaders of the photography pack, Canon and Nikon be introducing in-body IS in their higher end SLR digital in the future?  Only time will tell.
 Thanks to Michelle Waller for kindly allowing us to use these two images taken during a Bluedog Beginner Photography Workshop.

The above image was taken with the lens Image Stabilisation on and camera mounted on tripod.
The only difference in the image below is IS was turned off.

Photography by Michelle Waller

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