Friday, September 29, 2006

Camera Dust Removal And Sensor Cleaning

The Pentax K10D’s Dust Reduction features, like vibrating the sensor, the patented SP coating to inhibit particles from sticking, and the weather sealing are all great defensive steps against dust that sticks to the surface of a DSLR’s CCD. My Pentax *ist DS occassionally gets dust, so I’m jealous of the newer camera. But to me it’s just an intermittent hiccup in my picture taking activity over a span of months as long as I take simple precautions, just as I would with any other Pentax DSLR, with or without Dust Reduction.

I keep an easy going prevention routine that keeps me clean for a few months at a time, and only requires some vigorous dust blowing methods to dislodge whatever eventually comes along. But not everybody is so lucky. Sometimes the dust sticks like an 10 year-old boy to the wall at his first school dance. So, here are some tips and links that you may already be familiar with, but that every DSLR owner should have in their toolkit of dust removing resources.

Regular Maintenance

First, consider getting into the habit of rubbing the body of your camera and lenses clean from dust and finger oils with a microfiber cloth whenever it’s convenient. I have a large Pentax Optio microfiber lens cloth that felt too coarse to use on my lenses, but it's perfect for cleaning my camera. Consider that if the glass surface of your lenses are kept clean, the upkeep of the other surfaces should be the next priority. And it's not just for looks: if something's on your hands or on your camera, chances are it will get into the camera at some point. You don’t need to be anal retentive and clean everything compulsively every 5 minutes, or even every day of use. Just bear in mind that a clean camera exterior has some correlation to minimizing interior dust.

Giotto's Rocket Blower.

Using a dust blower regularly, especially when changing lenses, is the second line of defense. A few quick puffs over the inside of the camera and the rear of your lens whenever you change lenses helps a lot. Usually it's enough to blow out any major particles that could be a problem later on. This is different from using "Sensor Cleaning" mode on your camera (which lifts up the mirror), because you don’t want to expose the CCD unless you absolutely must. Just get a strong blower, such as a Rocket Blower or Hurricane Blower, then pump away.

Some people do these activities whenever they change a lens or when they're in a clean room at the end of a day of shooting. Just remember that you shouldn't use compressed air cans, or anything else than can blow either too strongly or too cool inside your camera because you'll risk damaging any number of parts (most compressed gas dusters should be avoided).

Preventive Manoeuvres

Make your lens changes in as clean an environment as you can. For example, some people will go back into their car rather than be outside, others shield themselves and the camera from the wind. Consider pointing the body face down whenever you have the lens off. Sometimes you need to weather proof your camera gear when you know you’re going out where it’s dusty, gritty or wet. There are lots of professional options, but don’t discount the cheap, tried and true method of a ziplock bag with 2 extra holes for the lensand viewfinder to pop out, and which you seal with some masking tape. It’s not hermetic, but you get the idea.

Seeing Dust

Unless you live in a protected lab, you're going to have to deal with dust eventually getting in your camera. Worse, dust wants to make sweet love to your CCD. Well, technically not your CCD, but the built-in glass low-pass filter that protects the CCD.

Aha! Sensor dust as seen in a photo of a clean wall.

I can usually first find dust in my pictures by noticing a small dark spot that shows up in multiple pictures even when the lens is clean. It’s more noticeable at small apertures and against light. So, to be sure, I take a shot of a white wall, or the sky, at the smallest aperture of my best lens (F22 of my 50mm F/1.4) and then usually it's pretty easy to see just how bad it is. It's most likely inside the camera over my sensor. The activated sensor has an electric charge that attracts dust to the glass of the low-pass filter, so dust in the chamber has the opportunity to fly around and stick there every time I take a picture. The K10D's SP coating on the glass reduces that problem, but all Pentax DSLR cameras before its arrival don't have that feature.

Dust that’s only visible through your viewfinder is likely stuck on the mirror. And if your mirror has dust that's not coming off, you really ought to think twice about doing anything about it. Unless you've got plenty of experience painting miniature portraits with a q-tip or were trained professionally, you're more likely to make things worse. These things scratch faster than Joan Collins.

Cleaning The Sensor

First, if there's stray dust in your camera, you're going to want to get it out without harming anything else inside. Your mirror and the CCD are especially fragile and can be scratched quite easily. Even the air you use can cause internal damage if it's too frigid or humid.

“Sensor Cleaning” mode involves activating the mode through the menu to lift up the mirror, removing your lens, pumping a dust blower repeatedly into the cavity over the sensor to dislodge dust, then turning the camera off (which brings the mirror back down), and replacing your lens.

Generally speaking, you may not need to invest in any other tools beyond a good dust blower if you find that using “Sensor Cleaning” mode dislodges the dust completely. But then if it’s really glued on, aka. “welded dust,” you have to decide if you want to do it yourself with off the shelf items (this includes getting a friend to do it for you) or paying a professional, such as sending it in to Pentax to be cleaned by their crew.

By the way, Pentax (if you decide to have them clean your camera’s sensor) will probably use tweezers to gently rub the CCD with a special lint free cloth that’s been moistened with a freon derivative - or so I’ve heard. This is pretty similar to using PecPads. But putting anything in your camera is something only a trained and practiced professional should do unless you’ve accepted that there's a good chance you'll scratch something and you're willing to take the risk. Similarly, some people have tried cotton swab applicators, which is like cleaning a Rembrandt painting with a mop: you have to be insanely careful.

Slightly more efficient methods involve squeegeeing the CCD with a plastic swab or spatula, or using brushes to whisk away the flecks, but each require a lot of care and attention (and risk aversion), and don't always work. Less careful people have used scotch tape or even their lens pens, but I don't think I would dare unless I was drunk.

There's lot's written on this subject, including stuff by manufacturers, so let me point you in their direction and encourage you to read widely on the matter:

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