Quote Originally Posted by Seb
I am both annoyed but relieved to know that this is the problem. In theory things should be fine as I did blowed air on the sensor (with an air blower that is) last night.

Just for the records could somebody explain me the link betwen aperture and the way dust actually appears on pictures?

thanks again

Seb
Aperture affects how much light is scattering on the back side of the lens. The larger the hole (like f/2.8) the more the scatter and thus the more the blur of the dust. When you have a small aperture (like f/32) the light is more finely focused and scatters less so the dust is blurred less and it become more obvious.

Think of it this way......hold your finger a few inches in front of your eyes. Look directly at it for a second. Now look past your finger at your monitor without moving your finger or head. Although not quite the same effect, it's very similar in the way it works.