Removing dust from
by Lorenzo Comolli
the sensors of DSLR cameras is a relatively new iussue, indeed in the
past the film cameras have not this kind of problems. It's bound to
happen that dust deposit on the surface of the sensor, and in this way
it projects a shadow in all the shoots. Indeed the dust deposits on a
protective glass, a few fraction of millimeters distant from the
sensor; for this reason the cleaning can be done without to much
troublings because you'll not really hurt the delicate sensor. The dust
shadows is more visible when we shoot using very closed aperture
ratios, because the projected shadow is smaller and sharpened; another
condition for visibility of dust is an uniform background, such as a
The measurement of dust quantity
Here the sensor was not so dirty, but two
small bristles are visible on the bottom. At left the raw image, at
right the enhanced one.
cleaning the sensor is fundamental to verify if this operation is
really necessary: some small piece of dust is normal and tolerable, and
it isn't worth to clean the sensor.
To examine how much dust is present you'll need an objective with a
very closed apertura: i.e. the Canon EFS 18-55mm, if used at 55mm, can
be closed at f/36. And more you'll need a uniform light source: a very
good source is a clear sky at zenith, but is't ok also a white sheet of
paper, defocused, or a flat-field-ometer like the one shown here below,
made for other purposes (obtain a flat-field for use with astronomical
CCDs). The result of such a test is in this figure.
My cleaning procedure
NOTICE: all the operations here described has been tested and never
damaged my cameras. However be aware that the author does not assume
any responsability for eventual damages to the reader cameras using the
procedure here described.
It's necessary to obtain the
- ethyl alcohol 90% (the normal
one, pink coloured), absolutely avoid the perfumed or diluted kind.
- a piece of absorbent paper (the
kind found in kitchen), turned two times
- some sticks with cotton wool at
Here is the procedure to clean the
The necessary stuff for
the cleaning, including my flat-field-ometer for capturing an uniform
All those operations have to be made very
quickly, I usually need a minute or so. I recommend to try before the
procedure on a less critical glass, like the front lens of an objective.
the shutter of DSLR camera with the sensor cleaning function, be
aware to use a fully charged battery. If the battery is discharged
you'll risk that the shutter closes when the cotton stick is inside....
visually if there are big particle of dust, be aware that almost
all the one visible in the test shots will not be visible with unaided
eye. I recommend to work under a strong light source and to avoid
speaking, and possibly breathe, to avoid spraying even more particles
on the sensor.
a little alcool on the absorbent paper, not very much.
- Roll over the paper an
extremity of the cotton stick, so that the cotton wool will be dampened. Be
aware that the cotton must not be very much wet.
- Now clean the sensor with the wet
cotton, with left-right and up-down movements, so as to clean uniformly
all the surface.
- Immediately after the cleaning,
and *before* that the alcool
evaporates, turn the stick and
repeat the movements with the dry cotton wool, so as to dry up the sensor without leaving
halos. Be aware not to touch with the hands the dry cotton in the
preceding operation, so as not to leave the greasy of the skin.
verify that no big dust particle is on the sensor, and if so,
remove them gently with the dry cotton stick. If the sensor is still
dirty, please repeat the cleaning with alcool and a new cotton stick.
the camera with the sensor toward the bottom, switch off to close the shutter and
finally... restart to breathe... ;-)
In the end you'll have to remount the objective on the DSLR and now
verify the sensor cleanness. If the sensor was really dirty, maybe
you'll need to repeat the procedure.
Here is the result of
the cleaning (at left a raw image, at right a very enhanched one).
This page explain how to clean the
DSLR cameras sensors with a very modest cost, and without so much
effort. On the market there are many special liquids and specific kits,
some of with very expensive and hard to import. My personal opinion, at
the light of the results here shown, is that they are not necessary.
For any comment, send me an e-mail: firstname.lastname@example.org