Sensor Cleaning Advice (from another place)
I was poking around "somewhere else" and noticed the following (which is copied verbatim except the names have been changed); maybe I should have put this under another more appropriate topic. 
Sensor cleaning
Hi
"I have had my camera (400d) for 6 months now. I guess I change the lens about once per week on average. I was wondering how often I should clean the sensor, or get someone else to do it for me? I don't seem to have a dust problem yet as there are no obvious specs on any of my photos."
Thanks, Pete
Answers
"If it ain't broke, don't fix it. Likewise, if you can't see sensor crud in your images, you don't need to clean the sensor". (Bob)
"No reason to clean a clean sensor". (Chuck)
"Do a few test shots at various apertures at a bright even subject (i.e. blue sky) to see if its visible. I personally only clean my sensor if I can see it at around f/5.6, or if there is dust at high volume at f/8. If you shoot landscapes, or anything else involving small apertures, you should clean more often. However, since you say you don't have any visible dust, listen to Bob". (Harry)
"Do you clean your car if it looks perfectly clean?" (Stan)
"I wouldn't even bother doing a test on it. If you only ever shoot at f/4 or wider and don't see crud in your pictures, does it really matter if you see crud in a test at f/22?" John
"Yeah don't worry about it. Even if there are a few specks of stuff, it won't show up until like f11 or more. If it starts getting bad, then check out www.copperhillimages.com
or google "copperhill method". There's an excellent tutorial on cleaning the sensor yourself on there and you can even order the cleaning fluid and stuff to do it yourself." Joe.
