Clean Your Camera Bag!
It's time to address a topic that goes mostly unnoticed: the dust and dirt that accumulates in the corners of your camera bag.
You've undoubtedly wondered where the dirt that gets on your camera's sensor comes from. You've learned to clean the sensor. You're careful when you change lenses, always doing so quickly and with your body shielding the open camera body from the wind. Yet still the annoying spots on your images come back sooner than you'd like. There's one source of dust and dirt you may not have thought of: the camera bag you carry all your gear around in.
Take a few moments right now and go get your camera bag. Open it up and take everything out of it. Just set everything on the table or even the floor for now. You can put it all back shortly. But first, look closely in the corners. If you shoot outdoors like I do, it's inevitable that you will accumulate at least some dirt in your bag. As you hike along with down the trail in search of great images, any dirt that does get into your bag with settle in the corners — all those nooks and crannies you generally don't pay much attention to. What do you do about it? Just use a vacuum cleaner to clean it out of course.
It may not seem like that small amount of crud is worth worrying about, but it just might be. As you hike along with your camera bag on your back or slung over your shoulder, at least some of those nooks and crannies this stuff can settle into could well include the edge of your lens cap and the bayonet mount where your lens meets your camera body. The next time you change lenses, that dust can get sucked inside your camera, and by now you know all too well where it can eventually land when that happens.
I've noticed that a lot of photographers are reasonably meticulous when it comes to cleaning their lenses and almost all are when it comes to keeping their sensor clean. Perhaps now a few more will be when it comes to their camera bags.