I’ve learned a lot about Digital Single Lens Reflex (DSLR) camera sensors and their foibles in the last few days.
Foible numero uno is dust. You don’t change sensors like you used to change film rolls, therefore dust that gets into the body will slowly (or not so slowly) accumulate on the sensor. If you live in a place like Atlanta that had a pollen count last week of 5,200 particles per cubic meter you may see a quicker accumulation than elsewhere (120 ppcm is considered extremely high. Yes, one hundred twenty). These dust particles will cause shadows on the sensor under the right (or wrong) conditions, leading to little black spots on your images. Not a high level of mojo, in my opinion.
With several very helpful suggestions from the Atlanta Flickr Group I ended up at cleaningdigitalcameras.com, which describes in exhausting detail the various methods and products to clean up a sensor that looks like this.
I obtained this image by opening up Photoshop to a new (white) file, setting the camera to f/22, exposure 2 seconds. I didn’t bother with focus and moved the camera around in a small circle during exposure to avoid picking up anything on my computer screen. After importing the image, I ran auto levels and voila! Dust.
What am I going to do about it? I ordered a Rocket Blower, Eclipse, and Sensor Swabs, with which I will clean my sensor in a week or so. Until then, I guess I’ll just deal with it.
For information, this article analyzes the various automatic dust removal systems for DSLRs by the big manufacturers. Boils down to: Olympus’ system works. Others don’t.