Tip of the day (Avoiding a dirty sensor)

If you’ve got a DSLR you’ve probably had the experience of uploading your photos onto your computer after a long day of photography – only to find that there are dark ‘spots’ and ‘blotches’ on your pictures.

These spots and blotches appear on all your shots in exactly the same position. They might be less noticeable on backgrounds with lots of detail (and more noticeable on plain backgrounds (like blue skies – especially when you have a small aperture) – but they’re there in all your shots (the picture to the left is one of the worst examples I’ve seen – and was the result of poor image sensor cleaning technique).

The reason for these marks is that you’ve almost certainly got dust on your camera’s image sensor.

Cameras are being developed that combat this problem (for example the Canon EOS 400D/Revel Xti and others) but until we all go out and upgrade our DSLR we’re all susceptible to it.

Most DSLR owners do eventually get some on your sensor (unless you never change your lens) but here are some tips for decreasing the likelihood of it:

  • Avoid changing lenses in risky environments (where there is wind, water, dust etc) – pick a lens and try to stick with it.
  • Turn camera off before changing lenses. On some cameras the sensor has an electric charge that will actually attract dust to it like a magnet.
  • Hold camera upside down (with the opening facing down) when changing lenses – it’s impossible for dust to fall into your camera if it’s upside down (unless there is wind that blows it up into it).
  • Have your lens ready when you’re changing lenses (be prepared and have your new lens ready to attach so that your camera is open for as short a time as possible).
  • Check your lenses for dust before attaching them – have a blower that you can get any specs off your lens with.
  • Clean your image sensor with care. There’s a lot of debate about whether to do it yourself or whether to get your sensor professionally cleaned (see below for of some of the DIY approaches to cleaning sensors) If you do tackle it yourself do so with extreme care – let the picture above be motivation to get it right!

To test if your image sensor is dirty photograph a white wall with a small aperture (large number) and you should see it in the images that result if you have any.