Who
knew that digital sensors would be magnets for dust? They are, acting like
little static electricity machines that attract minute and sometimes
grain-sized dust particles that are a pain in the neck. You can “spot” the
particles out later (which record as black dots and streaks) using cloning
tools and various healing brushes and blur tools, but the frustration of having
to spot images is simply 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 prevent dust from catching on the sensor in the first place.
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 where most dust problems occur. Turning your back on
the wind to shield the camera when changing lenses does not seem to help: if
you lack a changing bag, shielding it with a coat is better than nothing.
4)
If you like to photograph outdoors, when shopping for a camera get one with a
dust reduction (shake) system, and one that bills itself as having extra seals
to prevent dust.
This shot looks “innocent” enough and seemed fine when inspected on the LCD after exposure.
Later, with close inspection, the dust nightmare it contained was revealed. This was at the end of a long day’s shooting with a loaner camera and many of the images were unusable as a result. (Note: enlarge this image on your screen to see the blizzard of dust it contains.)
An experience like this should teach you a good lesson, as it did me. For some shots the dust had to be meticulously retouched in software. What a waste of time!
Note:
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 viewfinder pentaprism ( the
optical finder in DSLRs) or on the mirror. Check the lens, and if need be clean the front and rear element. Dust inside the lens cannot be cleaned without sending it to the manufacturer--this can be very expensive. If the pentaprism
has the dust it can be bothersome, but that dust will not show up on your
pictures. If it's on the mirror clean it very carefully with a commercial kit and remove the lens indoors to get access to the mirror--CAUTION: Be very tender when doing this as too much pressure or force could damage the mirror mechanism.
Mirrorless cameras, have no (optical finder) pentaprism or reflex viewing system. If the dust is not on the lens, any dust marks showing up on images means that there is dust on the sensor. Check and clean the lens itself first, both front and rear elements. Dust on the lens should be quite evident, as minute dust on the lens will usually not show up on the image.
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 playback menu, or download it
and enlarge it (though that might be too late for that day’s shoot). It can be
tough to see dust on your camera's LCD during playback. If you suspect you have dust, before
you go out on your shoot make photo of a blank white sheet of paper and enlarge the image
on a monitor. Move around it and enlarge
it to check—this will make the dust
spots quite visible.
If
you do have dust on the sensor try restarting the camera (if it has a dust
reduction 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. A few cameras have a "dust delete" protocol, which creates a kind of mask to spot out dust from a series of recorded images with the same dust pattern. I find this to be a very hit and miss affair.
Lastly,
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. You can send the body back to the manufacturer for
cleaning if need be, which is perhaps the safest route, or take it to a certified camera clinic. That’s your call, but if you clean it
yourself you need to use the camera’s self-cleaning setup (this is not available
on many cameras; if it is instructions will be available on the company's web site or in the instruction book) and be sure to use an AC adapter, because if the power goes
out during the process severe damage could result.
Get
in the habit of checking each time before you go on an extended trip. Checking
periodically, and especially if you have been photographing in the desert, at the
beach or in windy conditions.
