Watch out for this gotcha! It caught me out - so a warning, just something to bear in mind. I was using a Fuji X-E1 and 18-55mm lens but it will probably be a risk with any mirrorless camera especially with wide-angle lenses that have a rear element that comes close to the sensor.
I took some photographs on a misty morning and when I processed them I discovered large shadowy smudges down one side easily visible with the large areas of flat light grey. I thought it was dust (but looked a bit odd) or a mark on the sensor but I could not see it with magnification and cleaning achieved nothing