Lenses, sensors and dust spots

For most digital users, dust on the camera sensor is one of the easiest things to acquire and probably, the most annoying to live with.   There are variety of solutions but perhaps the best starting point on this topic is . . . . . prevention.

From the moment you remove a lens from a camera body, every grain of dust in your region will be rushing toward your sensor, at least that’s how it seems.  A few simple precautions will minimise the dust problem and thwart the dust’s ambitions.

Removing lenses:

  • Try to swap lenses as infrequently as possible
  • Try to remove lenses with a smooth action, any grinding of the lens mount against the camera body will create small metal shavings – these will head straight for the sensor
  • At the risk of stating the obvious, change lenses out of the wind and away from dusty areas
  • Switch the camera off for at least 10 seconds before removing the lens.  This will turn off the sensor and allow some of its static charge to dissipate.  Remember . . . static and dust get on well together
  • Point the camera at the ground when removing the lens, you’ll then have gravity on your side with regard to falling dust
  • Before fitting the new lens, blow gently across (not into) its rear elements to dislodge any existing dust
  • Adjust zoom lenses gently.  Any rapid pushing and pulling of the zoom mechanism turns the lens into a giant piston and in its travel from wide angle to telephoto, it can suck dust into the lens cavity
  • Fit the new lens and store the original lens in your camera bag, with body and lens caps fitted and then . . . . switch on.

If you have dust spots on the sensor, they will usually show up more starkly at small apertures (e.g. f16, f22 etc.) usually along the top edge of the image and in the sky areas.  Their removal is a three step process and with luck, you may see them off at step 1.

Step 1 – The Rocket Blower

Before you begin, consult your camera manual to find out how you can lock up the mirror for sensor cleaning.  In this mode, the camera’s mirror will flip up, the shutter will open and once the lens has been removed you will see the sensor which at this stage, will be turned off.   Ensure that you have a fresh, fully charged before using the mirror lock function. If the battery power is too low, then the mirror can lock itself in the up position and the camera will need to be returned to a dealer to reset the mirror.

You will now need a acquire blower which will a) give a good blast of air and b) have a filter in its base to prevent dust being sucked in between puffs.  I would recommend the Giottos – Rocket blower (cost around £10.00), it meets both of the above requirements.

Place the camera on a tripod with the lens facing slightly downward and ideally, work in a dust free area (the bathroom – following a bath or shower is often ideal).  Select the Menu option to lock up the mirror, carefully remove the lens, place the blower’s nozzle in the mouth of the lens mount and give several fast puffs of air.   Once done, lower the mirror and replace the lens.  To test the success of your blowings, take a photograph of a section of clear blue or white sky at around f16 or f22.  You may have to use manual focus, given that most autofocus systems won’t focus on blank areas – then examine the test image on your computer to check the sensor’s surface for dust.

If the dust is still evident . . . . . . .

Step 2 – The Arctic Butterfly brush

If the above hasn’t cleared the dust, then you will need to resort to one of Visible Dust’s products – the Arctic Butterfly brush. Available from Clifton Cameras for around £70.00

The brush is statically charged and comes mounted on a battery driven spinner handle.  When the brush is spun between cleanings, any dust is spun off and the bristles become re-charged with static.  To use the brush, repeat the above steps to lock up the mirror, then very carefully wipe the brush in one direction across the sensor.  Withdraw it, spin for 30 seconds and brush once more.  Drop the mirror, replace the lens and test as above for spots in the image.

and finally . . . .

If dust still remains lodged on the sensor, then wet cleaning is the final step.

Step 3 – Wet Cleaning

This latter stage requires some nerve and yet more money!   It’s as well to approach this stage with some caution because it involves wiping a moistened pad across the surface of the camera sensor and whilst it is wise to regard the sensor as being delicate and easily damaged, it does have a protective window (called a moire screen) in front of its surface and is reasonably robust.

You will need to buy some sensor cleaning swabs and whilst there is a bewildering array offered on line, I’d be drawn once again to Visible Dust’s products.  They seem to be the  market leader in sensor cleaning.  The swabs come either dry, or ready moistened and look rather like little cocktail stirrers.  Check out Amazon or Warehouse express.

They’re packaged in what seem like surgically sterile packs and can only be used only once before being discarded.  You must repeat the steps described earlier to raise the mirror and this time (whilst carefully following the supplied instructions) wipe the swab once across the mirror, repeating the process with new swabs as needed.

In most cases, the dust will be gone and no further wipings will be needed – well . . . . not until next time.  However, if stubborn marks remain, it’s likely that the camera will need to be returned to the factory or service dept.

Have a look on You Tube, where you’ll find hours of videos (usually made by very earnest men) showing how to do all of the above:

http://www.youtube.com/results?search_query=sensor+cleaning]&aq=f

I wish you luck!!

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