As I begin to get a little beyond the basics, there is one mystery which keeps popping up again and again. The attached files illustrate what is hard to explain.
S&S RDX-550D housing, standard flat port
60mm Macro lens
1x S&S YS-110a strobe
When processing my raw files in Lightroom, I often find mysterious large circles which are lighter than the surrounding area, especially in dark sections of the photo. Perhaps they are everywhere in the photos and only visible in darker backgrounds - not sure. These are distinct from normal backscatter. Sometimes i can just edit them out, but I'd really like to know why they occur in the first place. Are they a different type of backscatter? Are they because of unclean glass somewhere in the light path? Is at a fundamental flaw in my technique? I have seen them in others' online galleries, so whatever causes them, it's not unique to me.
"20131120-IMG_9966.jpg" is a hawkfish photo I was editing today when I saw the circles.
"circ1.jpg" is a crop of that pic with some of the mystery circles underlined (it's also been altered to make them more obvious)
I would love to know what causes this phenomenon and, more importantly, how to avoid it in the future.