Do you have dust on your DSLR sensor? Are you sure?
If you have more than one lens, the lens you need is always in the bag. Which means that you keep changing lenses, and dust will accumulate on the sensor, regardless of how careful you are. And how come they show up more on some images than other? There are two things which makes the dust stand out on an image: A uniform background, and a high F-stop.
Consider the following image, which was shot at F22. (I’ve added some contrast to make the dust stand out even more)
You see some of the dust quite clearly, while some are more hidden. Here are the ones I found:
Seeing the dust
But what if you want to check how bad it really is? Follow these steps:
- Make part of your computer monitor completely white. A simple way to do this, is to start a new document in Microsoft Word, or another text editor.
- Use a 50mm lens, or zoom to about 50mm.
- Set your camera to shutter priority (S, T or Tv, depending on your camera), and set the shutter speed to about 2 seconds.
- Set your camera to manual focus, and make sure that your computer monitor is completely out of focus. Remember that we’re not taking a photo of the monitor, but of the sensor dust.
- Aim at the white monitor, and take a picture, while you are moving the camera slightly. Again, we want to make sure we’re not taking a photo of the monitor, but of the dust.
Then bring the photo into Adobe Lightroom (or any image editor). Then turn up the contrast, and turn down the blacks. In my case I got the following image:
Pretty bad, huh?
Cleaning out the dust
So how do you clean out the dust? In general, I would recommend taking the camera into a camera store. They normally do this while you wait, and doesn’t charge too much.
The sensor is the most precious part of your camera, and if you get it scratched, you might as well throw away your camera.
Warning: NEVER USE COMPRESSED AIR, and NEVER TOUCH THE SENSOR WITH ANY PHYSICAL OBJECT.
What you need is a manual air blower, which looks something like this:
Here is what you do:
- In the camera menu, select the “Cleaning mode”. This will lift the mirror, and reveal the sensor.
- Remove the lens, while holding the camera downwards, to avoid additional dust from entering.
You should always keep your camera pointed down when changing lenses.
- Use a manual dust-blower, and blow upwards onto the sensor.
- Turn your camera off (which will lower the mirror) and replace the lens.