D600 OIL/DUST Report at 12,720 Shutter Count

Marc Heijligers wrote:

Expecting a 100% dust-free sensor is something that is not realistic. In practice, there will always be some dust on your sensor.

There may be dust on the back of your lens, on top of your mirror and in the compartment where sensor and lens are situated, that is floating around after cleaning (BTW, never touch your mirror when cleaning!!!). Some zoom lenses also have an air inlet, to keep the pressure constant inside the camera behind the lens, that may absorb some dust particles.

Whether the spots are related to the oil spots affecting new cameras out of the fab is something that is not very likely after so many shots. Underneath picture shows my D800 after a few 100 shots, the spots could not be removed with dry cleaning (so oily/greasy). After multiple cleaning at a Service Centre (needed to send it in a couple of times due to the left-AF problem), the camera is relatively dust-free, but not dust free (I've just looked, about 4 to 5 small particles). In practice I may see a particle in less than 1 out of a few hundred of pictures, so I choose to use the spot removal tool in Adobe Lightroom instead of fiddling with cleaning tools (which also may add dust instead of remove dust).

When the dust assembles over time, I'll send in the camera for cleaning at a service centre. If you suspect oil-spots, you can always send in your camera just before the warranty expires for a free cleaning.