A few weeks ago I was proudly showing my D700 pictures to a friend when he asked what were all these spots in the sky. I had noticed them before but presumed my lense was probably dirthy. Today, looking down the barrel of my AF-s 70-200 2.8GII, I noticed some flakes on the glasses inside the lense. Before blowing a fuse to the place I purchased my camera and lenses a month ago, I decided to do some test.
Shooting at an empty patch of sky, with both my 70-200 and my 24-70 at various focus and zoom setting both in Jpeg and NEF, I could clearely see dark circular spots, all at the same location in each pictures. Which lense or setting was used did not seams to make any difference.
Thinking the sensor was dirthy, I digg into the menu and do a sensor clean, then shoot again, surprise, the spots were still there but at slightly different locations. More cleans, more spots again at different location, slowly migrating to the right top corner. The number of spots seams to increase with the more cleans I do.
Then playing with ISO, I noticed that the spots were much sharper and smaller at higher ISO.
Anyone has a clue of what is going on?