The heart of any camera is the sensor. The computer is the brain but there isn’t a lot you can do as far as maintenance goes. Keep the firmware up to date and that’s about the extent of it.
But the sensor is another story. That’s where the images are being recorded and there’s a lot going on in the sensor bay. In most cameras there’s a mirror mechanism flipping up and down and those moving parts are lubricated at the factory. After that mirror flips up and down a couple thousands times, it sometimes happens that some of that sophisticated lubricant on the mirror mechanism ends up on your camera sensor.
Another way dust and dirt find their way on to your image sensor is changing lenses. No matter how careful you are changing lenses, short of a dust-free clean room protocol, sooner or later you’re going to get dust on your sensor. For some reason the most powerful attractive force in the universe for attracting dust is located in the sensor bay of your DSLR.
The day will dawn you start noticing spots in your photos. Little smudges that appear in the same spot photo to photo. The quickest way to check for grease and dirt is to go outside and shoot a patch of open sky at f/22. Then take the photo and jam the levels, you’ll see the smudges right away and clearly.
Okay, don’t panic. This happens to everyone sooner or later. You have several options for dealing with the problem, so just follow the protocol and you’ll be fine.
If you’re really worried, you can send your camera back to the manufacturer for cleaning. That will mean bouncing it across the country in a FedEx or UPS box and then the lab bounces it back to you. I’ve had cameras come back dirtier than they left, not because the factory guys did a poor job, but because of all the handling.
One gadget that’s indispensable is a lighted magnifier so you can see what you’re doing.
The other indispensable thing to have is a fully charged battery. If your battery dies in the middle of this operation, the mirror will drop back down, possibly on your cleaning tools. That will not make an improvement to the mirror mechanism. You will be sad.
Step 1 – Blower
The idea here is to see if you can dislodge the dust particle with a gentle puff of air. Do NOT get the tip of the blower too close to the sensor surface. Air at high enough pressure will mar the sensor cover. So just gently blow on the dust, it’s either going to come off or it isn’t.
Step 2 – Static brush
The next step is trying a specially made anti-static sensor brush. Do not use a lens brush! Sensor brushes are specially made.
Be really gentle. Anything that won’t come off with a gentle flick of the brush is probably lubricant.
Step 3 – Cleaning Kit
Lubricant is going to require a cleaning kit with methanol. Don’t mess around and try to cobble it together yourself. Spend the money and get a professional cleaning kit. There are detailed, step-by-step tutorials and instructions on their site. Follow them.
Take your time, don’t panic, and don’t try to cut corners and you’ll be fine.