IQ effect of dust on MFDB sensor?

[lowep]

How do small amounts of dust on a MFDB sensor effect image quality?

Does it make the image look soft/blurred/hazy/flat/deaden colors/leave tiny spots and specks like dust on film, or...

[theguywitha645d]

You see it in areas like the sky. Usually looks like oily or dark disks.

[lowep]

If sensor dust does manifest itself as distinctive spot(s) or shape(s) on the image rather than causing an overall effect (like the softening and/or reduced contrast you can get when the rear element of a lens is scratched) then it is probably one more variable I can eliminate from my troubleshooting list, so thanks for this useful reply :-)

[Paul2660]

Sensor dust on a Medium format sensor IMO looks just like dust on a 35mm sensor, round spots.  It's much easier to clean most a MF sensor since you can remove them  totally from the camera allow you to easily access all the tight corners. 
With Phase One, Capture One if you shoot a LCC during the shoot, you can use that to remove dust from the image much easier than using the normal dust removal software tools.

Paul Caldwell

[ced]

The IQ is not really affected but there are clearly visible circular spots/disks (mostly grey).
Sometimes they look like water marks on film and worm like if there is textile fluff on the sensor, they get worse the more you close down the fstop.