Ready to blow

With the mirror and shutter out of the way, the sensor is still protected. Your camera's sensor is too delicate to completely expose it to the elements, so it has a protective filter in front of it known as the Optical Low Pass Filter. When we talk about cleaning the sensor, we really mean the sensor's defensive filter.

The first thing to do is take your rocket blower and use it to gently blow dust and dirt off the surface of the sensor filter. Avoid touching the filter itself with the tip of the blower as this could damage it.

Always use the blower before swabbing or brushing the sensor. This is to ensure that you've removed any particles of grit, which are potentially worse than dust motes as they can scratch surfaces. A scratch in the sensor or lens could refract light and will leave a permanent ugly mark on images. Once you've blown dust off the sensor, you could also use a special brush to gently sweep the surface.

Never use compressed air on the sensor -- it will freeze on the sensor surface, possibly causing very serious damage. Always go with a mechanical blower, which will provide gentle, dry air to float those pesky dust motes away.