5D - strange image problems

[kbolin]

I just got my 5D and LUVIN IT!  Welcome back to true wide angle!

But, I've got a few images that have strange dark blemishes.  One on the top right and the other on the bottom left.  I was using a tripod and both images are ISO 250 @ 1/15th and either f25 or 36.  

There are only a few images like this and most are ok... similar in setup.

My only thought is that there may have been some dirt or dust on the filter and could have rotated around.

[BernardLanguillier]

It could be:

- dust on the sensor,
- dust on the filter, or any other part the lens (including the rear element). When using apertures as small as f25, these things do show up a lot more.

Regards,
Bernard