Does Your Sensor Need Cleaning?

How to tell

While preparing and packing for an upcoming trip, I decided it was a good idea to check to see if the sensors on my cameras needed cleaning. My usual indicator that it's time to do housekeeping is when I get back from a trip and find the dreaded blobs on a few hundred otherwise excellent images, so my smugness over actually doing something proactively prompted me to post this.

Sensor dust is easiest to see at small apertures so I created a plain white JPEG to display full screen on my monitor (white image link HERE - right-click and "save link as..."), cranked my lens down to f/22 with a slight underexposure and took a shot of the screen filling the entire image.

As you can see, my hunch paid off:
(No, there isn't a little arrow stuck to my sensor...)


All but the largest spots would be invisible in most images at wide apertures but if I were to stop it down to blur a waterfall or something like that, it would look like I shot it through the window of a gas station restroom! Maybe that's an exaggeration, but still...

What to do? 

1. You can take your camera to a local shop that offers sensor cleaning services. The going rates run from $40-$70.

2. Send your camera body in to a service center for about the same price plus shipping.

3. Do it yourself. (*GASP*)

It is actually not as hard or as scary as it sounds. True, if done with improper tools and materials you can make it worse than it was or even damage your sensor but with a little care and a moderate investment, you can save yourself some money and show up at every photo-op with a clean slate. So to speak. 

My weapon of choice has been the Visible Dust Arctic Butterfly 724 pictured here.

It has an ultra-fine brush that picks up dust with a static charge. The odd handle is the secret to the static charge. It contains a high-speed motor that spins the brush to build up the charge from the air around it. About 10 seconds worth will turn the fibers of the Butterfly into a dust magnet. It also does double-duty by ejecting particles from the prior cleaning during the spin. The cost is about the same as two cleanings at a shop.

Once you have the lens off, take a moment before activating the cleaning mode from the menu to use a bulb blower to blow excess dust out of the mirror box area and from the rear of the lens. This will help avoid re-contamination later. Do this holding the camera face down while blowing up into the cavity so dislodged particles won't re-settle inside. The Giottos Rocket is my choice since it has an intake filter to prevent sucking in dust and spraying it back on your lens or into your camera body.

DO NOT use canned air or even the specialized dry air CO2 dusters. There are a lot of delicate mechanisms in DSLR mirror box and anything more sharply focused and stronger than a bulb blower could possibly deform the shutter mechanism. Additionally, most commercial compressed air uses liquid propellants and a frigid stream of fluorocarbon accidentally washing across the sensor or mirror would be a bad thing.

After pre-dusting, activate the cleaning mode from the menu. This will flip up the mirror and lock the shutter open (or just the shutter lock in the case of a NEX or other mirrorless cameras). A fully charged battery is recommended to prevent the shutter from closing during the procedure. (Cameras that closely monitor charge levels won't allow the cleaning mode to even start with a low battery.) Take another moment to gently blow out the exposed cavity to remove any stray dust trapped behind the mirror (also with the camera face down). Set the camera down on its back and spin up a charge on the brush. Make a single light pass from one side to the other. Spin and repeat from the other direction. The brush itself is wide enough to cover the entire width of the sensor making the single pass the most effective method.

Check the results. To inspect the sensor, Visible Dust also makes a tool called a Sensor Loupe that is basically a side-illuminated magnifying lens designed to let you clearly see dust on the sensor. Opteka offers a less expensive alternative. If you elected to pass on the loupe, simply reattach the lens, turn the camera off and back on to deactivate the cleaning mode and take another test photo. Repeat as necessary until the blobs are all gone.

A few minutes and two swipes with the Butterfly...voila!

If you somehow got some particularly nasty particles on your sensor that resist brushing, you may have to resort to a wet cleaning which is a rather more delicate operation requiring specialized swabs and cleaning fluid. The need for this is far less common than a simple dusting so by the time you actually need to do a wet cleaning, your experience with the dry brushing may inspire you to attempt that procedure as well!

Happy (spotless) Shooting!