Avoiding camera shake with APS-C and APS-H cameras

A useful tip today for all you users of APS-C and APS-H sensored cameras (so the likes of EOS 7D, EOS 60D and EOS-1D Mark IV).

The rule of thumb to avoiding camera shake is to shoot at a shutter speed no slower than the reciprocal of the focal length of the lens. This means take the focal length of the lens, say 200mm, and then put a 1 over it so it looks like a fraction = 1/200. This now looks a lot like a shutter speed and gives you the steer that you should not use a shutter speed any slower than 1/200sec when hand-holding a 200mm lens that does not feature an Image Stabiliser.

However, while this guide was developed in the days of film (sorry about that pun!), it does not take account of digital cameras that feature smaller than full frame sensors. With these smaller sensor cameras, the field of view of the lens is narrowed and therefore any motion (like camera shake) during the exposure is more likely to cause camera shake. So what can you do about?

The answer is as simple as you’d hope!

Simply take the focal length of the lens and multiply it by the crop factor of the sensor – so an APS-C sensor camera is 1.6x and an APS-H sensor camera is 1.3x. Then use this as your focal length to find the reciprocal of.

So if we take our 200mm lens and put it on an EOS 7D (a 1.6x camera), the effective focal length is 320mm and so you should use a shutter speed of 1/320sec or faster. For an APS-H camera (like an EOS-1D Mark IV or EOS-1D Mark III), the effective focal length becomes 260mm. Since there is no 1/260sec shutter speed you should, according to the rule, use the next fastest shutter speed – again, this is 1/320sec. However, it is worth trying to shoot at 1/250sec to see how you get on – the 1/10sec may not be enough to cause you problems.

While it seems like an exact science involving fixed figures, the truth is this is a guideline and some of you may find you can handhold at slower speeds, while others will need to go up the scale to get sharp images.

If you’re using a lens with an Image Stabiliser, then you need to know the approximate effective range of the IS system built into your lens (typically between 2 and 4 stops) and then you can calculate back from the “non-IS shutter speed”.

If you think about this for a moment, you’ll realise this could be seen as a downside of smaller sensored cameras. In any given light level, they will need to use a faster shutter speed than a full frame model. All other things being equal, this will require either a more open aperture or a higher ISO setting. The irony is that the smaller sensors are less efficient at capturing light and therefore do not perform as well at higher ISO settings in terms of image noise…. something you may wish to take into account when choosing your next camera. If you plan to handhold then maybe a full frame camera is a better choice. Alternatively you can offset this to a degree with either a faster lens (a wider maximum aperture that lets more light in) or a lens with an Image Stabiliser built in.

How do you get on hand-holding? Does the rule of thumb work for you or are you more or less steady?