How to Prevent Sensor Dust Problems

Digital sensors are like little static electricity machines that attract minute and sometimes grain-sized dust particles of dust. You can “spot” the particles out later (which record on the image as black dots and streaks) using cloning tools and various healing brushes and blur tools, but having to spot images in this way is painstaking and not a good use of time, especially when the problem can be eliminated or diminished with a bit of care.

Manufacturers have not denied the problem and many cameras now incorporate dust “cleaning” systems that turn on every time you start up the camera. Generally these “shake” the sensor in the hopes of vibrating the dust off; sometimes this works OK and other times you might have to use more drastic measures. The best bet is to try to prevent dust from catching on the sensor in the first place.

All told, dust is pernicious and can work its way inside the camera in more ways than one: here’s some advice about keeping it to a minimum.

1) Always store the camera in a case or bag. It might look handsome on a bookcase or shelf but you are needlessly exposing it to ambient dust.

2) Never change a lens with the camera turned on. Having a charge across the sensor plane when it is exposed will act as a dust magnet.

3) If possible, change lenses inside a vehicle or changing bag, especially if there is any wind. This is when many dust problems occur. Turning your back on the wind and shielding the camera when changing lenses might help, although doing so when shielded by a coat is better.

4) If shopping for a camera, get one with a dust reduction (shake) system and that bills itself as having extra seals to prevent dust. These “dust-proof’ and “weather proof cameras” are worth it. And if you take lots of outdoor nature shots, especially in dusty environments, it’s a good idea to get well-sealed lenses as well.

This photo made with a loaner camera looks "innocent" of dust 

...but close inspection of the sky area reveals a dust nightmare. 

As an exercise I wouldn't want to repeat I enlarged the image to 100% on the monitor and worked with the clone tool and healing brush to eliminate all the lines and particles. Needless to say I won't be loaning from that service again. If you find similar problems send your camera to a reliable service center or the manufacturer and get that dust removed.

Checking for Dust

If you look through the viewfinder and see dust you might not have dust on the sensor—it might be on the lens itself or in the DSLR viewfinder prism or mirror. Check the lens. If the prism has the dust it can be bothersome, but that dust will not show up on your pictures. If the mirror has dust use a gentle cloth, gently, or compressed air.

Inspection

The only way to know if you have a sensor dust problem is to take a picture and inspect it by using the magnifying tool in your computer software—it may not how up on your small playback LCD. Download and enlarge your images at 100% (though that might be too late for a day’s shoot.) Another good test is to shoot a blank white sheet of paper, download the image, and move it around it to check the entire enlarged frame—this will make the dust spots quite visible.

What If You Have Dust?

If you do have dust on the sensor try restarting the camera (if it has a dust reducing system) a few times to see if you can have the system “shake” it away for you. If your camera has a “clean now”  feature you can use this instead of restarting it.

You can try cleaning the sensor yourself with commercially available kits, although I would caution you to be very, very careful if you go this route, as damage can easily occur. The best route for really bothersome dust (but isn’t it all) is to send the body back to the manufacturer or a certified repair shop for cleaning: this is the safest route. Many such services will do an overall check of the camera, including "pixel mapping" (identifying "dead" pixels) as part of an overall CLA (clean, lube and adjust).

Spotting with Dust Delete Programs

What if you have a precious and special image that simply can’t be reshot and you want to clean it of dust? Some manufacturers offer “dust delete” software for their camera cameras.

Here’s a typical dust delete procedure.

1) First, find where the dust delete setup is in your camera menu.

 2) Activate it and the self-cleaning procedure will start.

 3) Photograph, and fill the frame with a solid white object, like a sheet of copy paper. This photograph will not be saved to a card. The menu screen will confirm that is has “captured” the dust “data.” You then load and use the camera manufacturer software to automatically spot out the specks in your image. 

Note that this does not remove the dust but ID's the offensive dust and samples neighboring pixels to "spot" it out. You may have to go in and do additional spotting later. Yes, you can save one or a series of images this way, but don't go into the field without having the camera serviced.

Yes, you can spot and blur and the healing brush in software like Photoshop, but this can be painstaking for really dusty images. If you’ve ever tried to do that, you know what I mean. So, the best protection is to prevent dust from getting on the sensor in the first place, and checking periodically if the dust buildup is getting really, well, dusty.