I noted recently that my little 3-D stereoscope - I got it as a child - has been repeating itself over and over. I think it is a Déja-View Master... Those of you old enough to appreciate this will also like the next bit.
We get all sorts of service calls here for repairs and maintenance to digital cameras. One of the most frequent worries is material contaminating the sensor and showing up in the image. Here is a little guide to understanding what you see and what to do about it.
1. Vague grey blobs on an even grey ground are dust particles on the sensor - they shade the surface and thus it is darker, with a fuzzy outline. You may see a crescent-shaped item - likely a hair on the sensor.
You can clean the sensor yourself with a number of commercial brushes and swabs, but in the hands of the ham-fisted, this can carry a real danger of scratching the delicate surface. Ruin the sensor and you might as well buy a new camera...
Better plan is to let the technicians here at CE clean it for you. They do not ruin sensors, and the cost and time required for this service is not excessive. $44 for a small mirrorless camera, $55 for an APSC sensor, and $77 for a full frame DSLR.
2. The well defined grey blob with eight legs is a spider in a bathtub. Don't scoff - in 40 years in the trade I have seen a number of film and digital cameras infested with mites and crawlies of various types. Insecticide fumes and a mechanical cleaning get rid of them. If you discover a Huntsman in your mirror box, don't take off the lens, whatever you do...
3. We were asked how to get rid of this irregular-shaped mark on the image. If it is just one-off I would suggest Photoshopping it out with the clone tool. If you get a have a lot of these recurring, get yourself a Mossberg .410 and a box of No.7 shells.
4. This is harder to get rid of. And you get yourself in real trouble with the DCA if you try. Best idea is to turn away from it and photograph another bit of the sky. These marks rarely intrude themselves into interior shots or family portraits...