The easiest way to protect your sensor from dust is to prevent it from entering your camera in
the first place. Here are some steps you can take:
■ Keep your camera clean. Avoid working in dusty areas if you can do so. Make sure you
store your camera in a clean environment.
■ When swapping lenses, use a blower or brush to dust off the rear lens mount of the replacement
lens first, so you won’t be introducing dust into your camera simply by attaching a
new, dusty lens. Do this before you remove the lens from your camera, and then avoid
stirring up dust before making the exchange.
■ Minimize the time your camera is lensless and exposed to dust. That means having your
replacement lens ready and dusted off, and a place to set down the old lens as soon as it
is removed, so you can quickly attach the new lens.
■ Face the camera downward when the lens is detached so any dust in the mirror box will
tend to fall away from the sensor. Turn your back to any breezes or sources of dust to minimize
infiltration.
■ Once you’ve attached the new lens, quickly put the end cap on the one you just removed
to reduce the dust that might fall on it.
■ From time to time, remove the lens while in a relatively dust-free environment and use a
blower bulb (not compressed air or a vacuum hose) to clean out the mirror box area. A
blower brush is generally safer than a can of compressed air, or a strong positive/negative
airflow, which can tend to drive dust further into nooks and crannies.
■ If you’re embarking on an important shooting session, it’s a good idea to clean your sensor
now using the suggestions you’ll find below, rather than coming home with hundreds
or thousands of images with dust spots caused by flecks that were sitting on your sensor
before you even started.
Fixing Dusty Images
You’ve taken some shots and notice a dark spot in the same place in every image. It’s probably
a dust spot (and you can find out for sure using my instructions above), but no matter what
the cause, you want to get it out of your photos. There are several ways to do this. Here’s a
quick checklist:
■ Clone the spots out with your image editor. Photoshop and other editors have a clone tool
or healing brush you can use to copy pixels from surrounding areas over the dust spot or
dead pixel. This process can be tedious, especially if you have lots of dust spots and/or lots
of images to be corrected. The advantage is that this sort of manual fix-it probably will do
the least damage to the rest of your photo. Only the cloned pixels will be affected.
■ Use your image editor’s dust and scratches filter. A semi-intelligent filter like the one in
Photoshop can remove dust and other artifacts by selectively blurring areas that the plugin
decides represent dust spots. This method can work well if you have many dust spots,
because you won’t need to patch them manually. However, any automated method like
this has the possibility of blurring areas of your image that you didn’t intend to soften.
■ Try your camera’s dust reference feature. Some dSLRs have a dust reference removal tool
that compares a blank white reference photo containing dust spots with your images, and
uses that information to delete the corresponding spots in your pictures. However, such
features generally work only with files you’ve shot in RAW format, which won’t help you
fix your JPEG photos. Dust reference subtraction can be a useful after-the-fact remedy if
you don’t have an overwhelming number of dust spots in your images.
Cleaning the Sensor
whose advice you listen to. Some vendors countenance only dust-off cleaning, through the use
of reasonably gentle blasts of air, while condemning more serious scrubbing with swabs and
cleaning fluids. These same manufacturers sometimes offer the cleaning kits for the exact types
of cleaning they recommended against, for sale in Japan only, where, apparently, your average
photographer is more dexterous than those of us in the rest of the world. These kits are similar
to those used by the vendor’s own repair staff to clean your sensor if you decide to send your
camera in for a dust-up.
Removing dust from a sensor is similar in some ways to cleaning the optical glass of a fine lens.
It’s usually a good idea to imagine that the exposed surfaces of a lens are made of a relatively
soft kind of glass that’s easily scratched, which is not far from the truth (although various multicoatings
tend to toughen them up quite a bit). At the same time, imagine that dust particles
■ dSLR Quirks and Strengths
are tiny, rough-edged boulders that can scratch the glass if dragged carelessly across the dry surface.
Liquid lens cleaners can reduce this scratching by lubricating the glass as a lens cloth or
paper is used to wipe off the dust, but can leave behind a film of residue that can accumulate
and affect the lens’ coating in another fashion. Picture the lens wipes as potential havens for
dust particles that can apply their own scratches to your lenses.
You can see why photographers who are serious about keeping their lenses new and bright tend
to take preventive measures first to keep the glass clean. Those measures often include protective
UV or skylight filters that can be cleaned more cavalierly and discarded if they become
scratched. If all else fails, the experienced photographer will clean a lens’ optical glass carefully
and with reverence.
Most of this applies to sensors, with a few differences. Sensors can be affected by dust particles
that are much smaller than you might be able to spot visually on the surface of your lens. The
filters that cover sensors tend to be fairly hard compared to optical glass. Cleaning a sensor that
measures 24mm or less in one dimension within the tight confines behind the mirror can be
trickier and require extra coordination. Finally, if your sensor’s filter becomes scratched through
inept cleaning, you can’t simply remove it yourself and replace it with a new one.
In practice, there are three kinds of cleaning processes that can be used to vanquish dust and
gunk from your dSLR’s sensor, all of which must be performed with the shutter locked open:
■ Air cleaning. This process involves squirting blasts of air inside your camera with the shutter
locked open. This works well for dust that’s not clinging stubbornly to your sensor.
■ Brushing. A soft, very fine brush is passed across the surface of the sensor’s filter, dislodging
mildly persistent dust particles and sweeping them off the imager.
■ Liquid cleaning. A soft swab dipped in a cleaning solution such as ethanol is used to wipe
the sensor filter, removing more obstinate particles.
The first thing to do is to lock up your camera’s mirror so you can gain access to the sensor.
You’ll probably have to access a menu item in your dSLR’s setup page to lock up the mirror.
Some vendors recommend locking up the mirror for cleaning only if a camera is powered by
an AC adapter, rather than by a battery. The theory is that you don’t want your battery to fail
while you’re poking around inside the camera with tools. A damaged mirror, sensor, or both
can easily be the result if the mirror flips down before you’re finished.
In practice, my digital camera’s battery poops out less frequently than I experience brownouts
and AC power blackouts. My recommendation is to charge your camera’s battery and use that
with confidence to keep your mirror latched up. That recommended AC adapter may be an
extra-cost option that you’ll buy and then not use for anything else (unless you do a lot of work
in a studio).
Once the mirror is up, you should work as quickly as possible to reduce the chance that even
more dust will settle inside your camera. Have a strong light ready to illuminate the interior
of your camera. If you happen to have one of those headband illuminators that blasts light anywhere
you happen to be gazing, so much the better.
The next few sections will describe each of these methods in a little more detail.
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