I've heard that some of the Canon cameras, including the 5D, occasionally have a problem with lubricant coming off the mechanicals and getting on the sensor. It appears I have got the granddaddy of this kind of problem.

Within the past month or so since I got the camera new I've had to clean the sensor several times -- not because of dust but because of tiny smears that magically appear. I must have spent $100 on various swabs and pads and other Visible Dust concoctions -- and I've never been able to get the sensor completely clean. There are always faint blobs somewhere (and yes, I've followed the directions to the letter.)

I also bought one of those mirror chamber cleaning kits and did that as well. But no matter how clean I get the sensor, after shooting a hundred or so frames new blobs appear.

Since I haven't been changing the lens (I leave the 24-105 on all the time) I'm sure the problem is not from the outside.

I'm going to send the camera to Canon to have it cleaned. But before I do I'd like to know if anyone else has had this problem and, if so, how did you handle it?

Thanks.

I did not have a problem with the 5D, but did with my 1DII...although not nearly as severe as what you describe. Some type of oily substance was getting onto my sensor brush's bristles and then getting smeared across the sensor. The problem eventually disappeared after several cycles without Canon's intervention. But its specific cause remains a mystery to me.

Good luck with this.

Maybe you shouldn't store the sensor brush in the olive oil bottle?

Anyway, I'm delighted that my 5D hasn't exhibited such symptoms (yet).

There was at least one previous discussion about this problem on the site. You might want to do a search.

Have a look here

Photonotes.org

9 months out and my 5D has no oil or dust problems with VF or sensor. I've not heard of oil problems before so this may be somewhat rare. Mostly guys complaining about VF or CMOS dust.