I have a really nasty looking piece of dust on my 550D's sensor, situated in the top right-hand corner of each image I take with anything higher than f/11. I am going to get a decent sensor cleaning kit, but I'd like to know which corner of the sensor should I focus on to get rid of this annoying particle?

In other words, does a lens flip the incoming light from left to right and turn it upside down? I think that's correct, so that means the answer in this diagram will be A, correct?

enter image description here

And before anyone asks - yes, I will clean the entire sensor while I'm in there, but this will help me focus on this particular (pun intended) problem. Thanks in advance!


1 Answer 1


C is the correct answer.

Well, actually it's A if you look at the sensor from the back, but my guess is that you will turn the camera around and access the sensor from the front. So it's C.

  • 1
    \$\begingroup\$ An old photographer's bad habits -- not only do I still expect the back to open, I can't help flicking the advance lever that isn't there anymore. This should be the selected answer -- I'll flag mine for moderator action. \$\endgroup\$
    – user2719
    Commented Dec 21, 2011 at 15:24
  • \$\begingroup\$ Thanks Edgar and Stan - I will switch my accepted answer. Much appreciated! \$\endgroup\$ Commented Dec 21, 2011 at 15:31
  • \$\begingroup\$ I didn't know you could do that -- I've never asked a question on SE, except on Meta where a definitive answer from one of the chief cooks and/or bottle-washers was provided. (You don't not accept a policy explanation from Jeff.) \$\endgroup\$
    – user2719
    Commented Dec 21, 2011 at 15:41

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