Internal dust in focus?

[kenneth_smith7]

<p>I'm using a Nikon PB-5 bellows with a Micro Nikkor 55mm @ f/11. Exposure is with flash. Nikon D600.<br>

What I thought was sensor dust turns out to be something utterly baffling. Is it possible that I'm focusing the internal lens dust? The camera sensor checked out O.K. It had a few soft spots, but nothing like the hundred or more hard black dust spots that clog both ends of the frame length wise. I'm using a focus staking technique and noticed that the out of focus areas have sharper dust spots, and they are many. What to do? I'm truly surprised to discover this problem, and it occurs with both the d7000 and the d600. I don't think it's the camera. </p>

[geoffm]

<p><em>Could it be internal lens dust?</em> Extremely unlikely! I cannot imagine how any set-up could produce sharp spots from dust on or in the lens.<br />Anything that produces a hard clear black spot is going to be on, or very close to, the sensor (i.e. on the anti-aliasing filter.) My guess is that the extremely small effective aperture that you get using a bellows is showing up sensor dust that you simply don't see at more conventional apertures. You may end up pushing the limits of sensor "cleanability"! :-)<br>

(However, if you tell me that the dust spots are in <em>exactly</em> the same positions with both cameras, I'll retract the above and rethink!)</p>

[ShunCheung]

<p>This question is cross posted to the Nikon Forum: <a href="/nikon-camera-forum/00cKlj">http://www.photo.net/nikon-camera-forum/00cKlj</a></p>