The surface of a DSLR camera’s image sensor may get dusty easily due to the interchangeable structure of the lens. Nonetheless, we can maintain a clear image quality if we clean it correctly and regularly. In this article, I will explain how to do so. (Reported by: Ryosuke Takahashi)
An example of a photo taken with dust on the sensor. (Dust spots circled.)
How to tell if there's dust on the sensor?
When dust gets onto the surface of an image sensor, the position where it is located is not exposed and appears as a black dot in the resulting image. Such black dots show up clearly particularly when we are using a wide-angle lens. Also, the shape of the dust will be captured more sharply the narrower the aperture used.
However, if we think of it the other way round, we can actually make use of this characteristic to promptly discover dust on the image sensor surface that would otherwise be hard to detect. As illustrated in the example below, use a wide-angle lens or a zoom lens with the focal length set to the wide-angle side and open the aperture to its maximum. Point the camera at the sky, take a shot, and you will be able to tell from the resulting image whether there is dust on the sensor.
If dust is present, perform sensor cleaning to remove it. There are two ways to do this. The first is to make use of the auto cleaning feature on the camera, and the second is to clean it using a blower with the mirror flipped up.
Set the focus manually to infinity, or establish focus on a cloud or any other object that is easy to focus.
How to remove dust from the sensor?
 Removing dust using the "Sensor cleaning" feature on the camera
From the Set-up menu, select "Sensor cleaning".
Select "Clean now" from the options available.
When you see this message display, select "OK" and press the SET button.
A "Sensor cleaning" graphic illustration will appear, and cleaning will start. The sensor will vibrate to shake off any dust attached to its surface.
 For dust that cannot be removed with "Clean now"
Select "Sensor cleaning" in the Set-up menu, followed by choosing "Clean manually".
A brief description appears, explaining the steps to perform cleaning manually. Read through the steps carefully and select "OK" before detaching the lens.
Detach the lens and blow off dust with a blower (*ensure that the tip or any part of the blower does not come into direct contact with the sensor). After you have finished cleaning, attach the lens and turn off the power of the camera to restore the mirror to the original position. Cleaning is now complete.
If dust is found on the surface of the image sensor, you can remove it using either the "Auto cleaning" feature on the camera or by following the steps shown in the "Clean manually" option. For dust that cannot be removed with the "Clean manually" option, do not try to remove it yourself forcibly. Bring the camera to a Canon service centre and have it cleaned by our professional staff. The surface of the image sensor is extremely delicate. Do not wipe it with a cotton bud or any similar objects.
Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China. Takahashi is a member of the Japan Professional Photographers Society (JPS).