We start by answering some of the most common questions photographers have about camera shake and then show you a few simple methods for controlling it.
Why are my photos blurred?
There are a number of reasons why images end up being nowhere near as sharp as they should be. The quality of the lens attached to the camera plays a part, as of course does the accuracy with which it’s focused.
However, the chief culprit for soft shots is more than likely to be camera shake. Whether this shake is the result of a heavy camera and lens or a long exposure in low light, the effect is the same: a picture that lacks bite.
The extent of the blur largely depends on the shutter speed used at the time: sometimes a slight loss of definition will only be apparent when you magnify the picture during playback.
Why is shutter speed so important?
As we learned last issue, the choice of shutter speed dictates how long the camera’s imaging sensor is exposed to light in order to record a picture.
Naturally, if there’s not much light available, such as when you’re shooting at sunset or indoors, the exposure will take longer and this increases the risk of blurred pictures.
While it may seem obvious that it’s hard to hold the camera steady for a five-second exposure, it might be surprising to learn that even an exposure measured in fractions of a second – whether that’s 1/10 sec or 1/100 sec – can also show the effects of camera shake.
To minimise the risk, you need to consider the focal length of the lens when working out what your ‘safe’ handholding speed is.
How does the choice of lens make a difference?
Shorter lenses are typically easier to hold steady than longer lenses. As well as being heavier and more cumbersome, lenses with longer focal lengths also offer greater magnification.
This means that even a slight movement will be equally magnified: look through the viewfinder as you hold a 20mm lens unsteadily and you’ll see a little movement; do the same with a 200mm lens and chances are that you’ll lose the subject from the viewfinder altogether.
The rule of thumb to achieve sharp photos is to ensure the shutter speed doesn’t drop below the effective focal length of the lens. For example, if you attach a 50mm lens to a full-frame camera, you wouldn’t want the shutter speed to be slower than 1/50 sec.
What do you mean by ‘effective’ focal length?
Most digital SLRs use an APS-C sized sensor that’s smaller than a full-frame one, and consequently a smaller part of the subject or scene will be recorded.
You’d need to fit a longer lens to a get an equivalent view with a full-frame SLR, so this should be factored in when working out the minimum handheld shutter speed to use with an APS-C SLR.
By multiplying the focal length by the ‘crop factor’ of the smaller sensor – usually x1.6 (for Canon cameras) or x1.5 (for Nikon cameras) – you get the effective focal length.
A 100mm lens used on a full-frame camera should give sharp pictures at 1/100 sec or faster, but the same lens fitted to an APS-C camera would need a shutter speed of at least 1/160 sec (100 x 1.6) in order to reduce the effects of camera shake.
How do I get a fast shutter speed?
The more light there is, the more likely it is that you’ll be able to use a fast shutter speed. However, you can also achieve shorter exposure times in low light by dialling in a higher ISO sensitivity or a larger aperture.
High-end lenses offer maximum apertures in the region of f/2.8 or f/1.2, making it easier to eliminate camera shake – on paper at least.
In reality, these lenses are actually often much heavier than ‘consumer’ lenses, so good handholding technique is still required.
I’ve got an image-stabilised lens – does that help?
Yes, it does. An image-stabilised lens features gyroscopic sensors that detect which direction the lens is shaking in, and continuously adjust the position of some of the internal lens elements to compensate for this movement.
Image stabilisation has come a long way, and the latest stabilised lenses offer up to four stops of correction. In other words, you may be able to get sharp results at shutter speeds that are four stops slower than the recommended handheld shooting speed.
That 100mm lens? Instead of sharp pictures at 1/160 sec, you could potentially get shake-free shots at up to 1/10 sec by using image stabilisation.
However, even an image-stabilised lens requires good handholding technique. It can only correct for slight vibrations rather than full-scale wobbles, and besides, everyone’s mileage varies when it comes to keeping a lens steady.
Some photographers can get sharp pictures using exposures that are longer than the ‘safe’ handheld shutter speed for a particular lens, while others can only get consistent results at a shutter speed that’s twice as fast as the recommended one.
How can I improve my technique?
The key is to support the lens with one hand, rather than gripping the camera body with two, keep your elbows in and press the shutter release gently.
Make use of any natural support you can find too. Resting the camera and lens on a fence post or bracing yourself against a wall will give you extra stability and sharper pictures, particularly when combined with image stabilisation to soak up any slight vibrations (see also More ways to hold a camera steady when a tripod isn’t possible).
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