Why am I getting nasty dustspots and what can I do?
I've been shooting RAW photos with a Nikon D300 / Sea & Sea MDX-300 setup / 2 ys-110 alpha strobes / TTL converter. Generally, I have been intentionally underexposing most of my shots, especially when taking pictures of light objects on a colorful background. When I bump up the exposure of the photos, however, I get big, nasty dust spots that weren't visible until I loaded these up on a PC and tried to edit the photos. The D300 has a self-clean feature for dust, which unfortunately I did not use until I got back from my trip and saw the pictures on a big screen. I'm not sure if the dust spots are from the sensor or from the lens, which I carefully rinsed in large, fresh-water, photo-only tanks for several hours each eve (and for a shorter time after each dive). Anyway, 100's if not 1000's of photos with this problem...
Is this a lens cleaning issue? A sensor issue? A problem with my technique (of underexposing and then bumping up)? What are the best practices in cleaning port lenses?
One thought is that the problem came from using a 60mm lens in a macro port that was meant to work for a 60mm or a 105mm, so the face of the macro port was a fair distance from the end of the 60mm lens.
Thanks for any advice!
PS 3 examples attached. I know that taking a picture of a black frogfish is nearly impossible anyway... this one just illustrates the problem nicely. The barracuda may just have been too far away (and not sure the flash fired). Again, it just illustrates the problem.
