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Dust and digital photography

An annoyance that is hard to avoid.


A low pass filter sits in front of a dSLR's imaging sensor.
A low pass filter sits in front of a dSLR's imaging sensor.

Dust has plagued the photographer since the beginnings of photography. Dust on memory cards, dust on film, dust on negatives, dust on lenses and dust getting into cameras and camera bags.

You may be surprised to learn that there is increased risk of dust contamination with digital photography, notably with dSLR (digital single lens reflex) cameras that have interchangeable lenses. The most common way dust gets into a camera occurs when the lens is removed, even for a couple of seconds. When there is an electrical charge within the camera, it will actually attract dust, drawing it in like a magnet.

There does not need to be a dust storm for it to be a problem; the normal atmosphere contains enough dust for the photographer to need to take precautions against it.


With film, dust would typically affect only that one frame on which it had settled. Dust on a digital camera’s imaging sensor (more accurately, on the low-pass filter that is in front of the image sensor) will remain there until it is removed, affecting every picture captured by the sensor.

LOW-PASS FILTER
In a dSLR, one or more low-pass filters are located in front of the imaging sensor to:
  • - allow the lowest-frequency waves through and cut off the highest,
  • - resolve aliasing that causes jagged edges when photographing circular objects and diagonal lines, and
  • - to protect the sensor from dust (most have an anti-static coating to discourage dust from sticking).

  • Dust in your camera shows up as spots in an image.
    Dust in your camera shows up as spots in an image.

    You will know that your sensor is contaminated with one or more dust particles when you examine your photographs on a computer, especially images you took using a small aperture, although a severe dust problem may sometimes be noticeable when reviewing images on your camera. But, smudges or apparent dust that you can see on your camera’s monitor or viewscreen are more typically from dust or even water droplets on the front element of your lens or on a filter attached to the lens. Clean the lens before jumping to the conclusion that your image sensor has collected dust.

    When viewing your images on a computer, look first in sky areas or other relatively large areas having the same tones for evidence of dust contamination. The dust will appear as dots or slightly larger spots of a different tone, usually somewhat blurry, but not always. They might sometimes appear as well-defined spots. Other areas of an image may have been contaminated by dust specks, but may not be as noticeable if the areas are multi-colored or have a variety of highlights and shadow areas. (These spots are actually caused by a shadow from the dust when light passes over it and strikes the sensor.) Dust spots will appear in the same location from frame to frame.


    The good news is that dust can be removed from a sensor filter, preferably by having it professionally cleaned. You may also be able to clean dust from your camera’s image sensor filter yourself using a special kit and setting your camera to its sensor cleaning mode, but you must take great care when doing so to avoid causing damage.

    Your camera’s manual is where to look for the manufacturer’s approved method for cleaning dust from the sensor filter.

    If you are at all uncomfortable about your ability to properly and carefully remove dust from your camera, don’t attempt it; have an authorized service technician take on the job. You can irreversibly damage your camera by improperly attempting to clean it.

    The manufacturer’s approved method for cleaning dust from the sensor filter can be found in your camera's manual.
    The manufacturer’s approved method for cleaning dust from the sensor filter can be found in your camera's manual.

    The clone tool or clone stamp copies a portion of an image so you can paste it over another area of the image. It is exremely useful in the removal of dust spots.
    The clone tool or clone stamp copies a portion of an image so you can paste it over another area of the image. It is exremely useful in the removal of dust spots.

    REMOVING DUST SPOTS FROM YOUR IMAGES

    You can also remove dust spots from your images after the fact on your computer, using an image-editing program like Adobe PhotoShop.

    The most popular tool for this simple task is the clone tool, which you would use to copy a spot-free portion of a picture and then transfer it to cover over the place where the dust spot is located.

    AVOID DUST IN THE FIRST PLACE

    You are better off to take steps to keep your sensor dust free from the start.

    Begin by never leaving your dSLR camera anywhere, not even for even a second, without a lens or a protective cap attached.

    When you change lenses, do so as quickly as possible, and do it in as clean and dust-free (and moisture-free) an environment as possible. The lens that is going to be placed on the camera should be out of its case or your camera bag and have its rear cap already removed so that it is ready to be attached to the camera body in a smooth, quick motion as soon as possible after the other lens is removed from the camera.

    If the environment is dusty, windy or damp, move your camera to a cleaner environment before interchanging lenses.

    If you can’t do that, place the camera inside a protective bag, even a plastic garbage bag or your camera bag if it's large enough, to minimize the potential for dust contamination when changing lenses.

    If you know you will be taking pictures in a dusty place, switch to the lens you think you will be using before you reach the destination.

    Even after following these precautions, it is inevitable that some dust will enter your dSLR camera over time. When it becomes noticeable in your images, it's time to have the camera cleaned.


    The main concern regarding dust contamination in photography is dust within the camera, which we discussed above. But, dust also settles on the camera's exterior and on the outside of accessories and other equipment we use in taking photographs.

    It doesn't take more than common sense to dust off your equipment before you use it and before you put it away for the day.

    Many photo assignments we take on can occur in dusty environments - the beach, for example, or a windy site in the desert, on a dry dirt road in summer or at an outdoors sporting event. Dust can even work its way into a vehicle in which you have placed your camera bag as you drive down a back road in the countryside. You may not even notice it until you arrive at your destination, when you become aware that your gear has a coating of the dreaded stuff on it.

    This dust can actually damage your equipment as you handle it. Ideally, you would have a vacuum cleaner handy to run it over your gear and suck up the dust before you use it or store it away. Even better, though, is to protect your camera and other items in the first place, by wrapping them in plastic or keeping them in a dust-proof (and water-proof) bag or camera case.

    You should always carry lens and camera cleaning tools with you so they are available when called for. Keeping your equipment free of dust and grime will keep it serviceable for years to come, rewarding you with contamination-free photographs.

    Over time, the sensor can accumulate quite a bit of dust if left uncleaned. It is annoying and tedious to have to remove its spots digitally from almost every photo you take.
    Over time, the sensor can accumulate quite a bit of dust if left uncleaned. It is annoying and tedious to have to remove its spots digitally from almost every photo you take.