If you look closely enough at photos taken with a digital single-lens reflex (SLR) camera that's been used for a while, you'll probably see the dark silhouette of sensor grime. These opaque specks — the result of dust and detritus that has settled inside your camera's body — can become recorded into photos, permanently fuzzing or blocking parts of the image.
Even if you never change lenses, dust can still drift into a camera body and land on the sensor, causing this speckling problem. And even bigger particles can easily reach the sensor if you do swap lenses. Some advanced digital SLRs now offer auto-cleaning modes that try to shake these particles loose. Such features help, but they're often not enough to ensure blemish-free photos. Here's how to manually do the job of cleaning your DSLR camera's sensor — safely and effectively.
A number of DSLR cleaning products are available to choose from. Many of the kits can be overkill, including those with vacuums and other nice-but-unneeded tools. One optional extra I do like, the Delkin SensorScope, acts as a magnifying glass to identify debris.
High-end tools like these are convenient, but I'll show you how to test the sensor without buying an expensive gadget. Instead, start with a basic swab-and-fluid kit before considering upgrades. I prefer the Photographic Solutions Digital Survival Kit because of its no-frills approach and low cost. Just be sure to pick the right version of a kit for your specific camera, because some fluids react badly with some sensors. Consult the kit manufacturer's Web site to find the right kit for your camera. Also verify that the swab size matches your camera, so you don't end up with something too big.
Before you begin, it's important to note that the sensor-cleaning process can damage your camera if you use the wrong tools. If you follow your cleaning kit instructions precisely, you should easily make it through without any problem.
But don't clean the sensor if the lens is the real culprit. Use a blower to puff any debris off the front of the lens, and follow up with a nonabrasive cloth. Use the same technique on the inside of the lens, where it mounts to the camera. Liquid cleaners can damage lens coatings — never use an off-the-shelf household cleaner. If required, apply a cleaner that's specially formulated for camera lenses.
Locate the dust
Now, here's how to test the sensor before cleaning it. In an area with lots of light, set your camera with as small an aperture as the lens allows. Focus on a blank, white surface like a sheet of paper, and use the aperture-priority mode so that the camera automatically sets the proper shutter speed. Fire some test photos to use as pre-cleaning, "before" images. These will help you spot dirty areas on the sensor and will also give you a point of comparison after you've finished cleaning.
Open the test images on your PC, and zoom in at 100 percent to show one photo pixel per one display pixel. These photos should show the same even, white surface that you photographed.
Look for tiny, translucent droplets, dark specks, or thin lines. Clothing fibers, hair, pollen, and environmental debris can leave these marks. If they appear in the same position across all photos, a dirty sensor is the culprit. (If you don't see any dots at all, stop here, because that means your sensor is already clean.)
Clean the sensor
Activate the camera's manual cleaning mode to flip open the mirror, and then remove the lens. Be sure that the battery is fully charged — or work with an AC adapter — because the mirror or prism will slam shut when the camera loses power or is turned off. You can damage the camera's optics with your cleaning tools if they get in the way.
If you can clearly see something on the sensor, try to knock it off with air from a squeeze-bulb blower. Open a new sensor swab, and add two or three drops of the Eclipse solution to the tip. With a little sweeping gesture — gentle but firm — drag the swab laterally across your sensor. Twist the swab 180 degrees and drag it across in the opposite direction so that the clean side is leading the second pickup. Throw out the used swab.
Reattach the lens, and close the mirror or prism. Shoot additional test photos to see if you cleared out all of the debris. If not, repeat these cleaning steps until the sensor shines.
If you're away from home — especially if you're outdoors — don't try to clean the sensor directly. Instead, puff a few gusts from a bulb blower into the camera without making physical contact. Save the direct cleaning for when you're back in a controlled environment.
Keep the sensor clean
The best way to keep the sensor as clean as possible is to be mindful of your lenses. Swap these attachments quickly, keeping the camera body and both sides of the lens capped when not mounted together. If you have extra body- and lens-socket caps, lock them together in storage to block outside elements. The longer any one of these surfaces is exposed, the more likely it'll gather grime.