Truly my camera hates me
So many of us are very familiar with sensor aids, those wonderfully awful spots and smudges in the smooth swathes of blue in our sky. The spots come from dust and other particles resting on our sensor. They show up at smaller apertures and easiest seen in areas of continuous tone (hence why they're commonly scene in the skies of landscapes). For macro, where we find ourselves descending to smallest of apertures to give us all the depth the lens can muster and even then suffer from the shallowest of dofs giving us creamy bokeh the problem becomes most acute.
In the example to the left is a particularly bad case. It was also cleaned with large printing in mind so fainter and smaller particles had to be removed then you would have to for web presentation. When you darken areas the dust becomes further apparent. There several tools available to us to expedite the process. Both in camera and in image processor are tools where you can record dust data which can automatically deal with the worst of it. The finer grains still need to be done manually and the processor can make poor healing choices (especially if it's cleaning up over a detail area). You can also clean your sensor. Using one of those hand-squeeze blowers you can knock the worst off and if you have the gumption you can could wet clean your sensor with the swabs available on the market. Regardless, if you shoot macro be ready to spend some time cleaning the image.
How bad is your camera aids?
Curious to know if you camera has it bad? Here's an easy way to check.
1) Pick a lens that you have with with smallest aperture (probably f22 or f32) and set it to that
2) Turn off auto focus and focus the lens to as a close a distance as you can (aka macro focus)
3) Pick an even white surface like a wall or sheet or paper and move a few feet away placing it well out of focus
4) Take a shot and pixel peep away on your computer