It's "purple fringing", a lens aberration. It's most prevalent at wider apertures and between areas of high contrast. The very bright white object next to a dark background plus shooting wide open would be a perfect example of where this would occur. Many/most lenses have at least some aberrations.
>Does what you see here look like "some" or a lot. >Seems that out of the three Nikon lenses that I have, only the >18-55 kit lens isn't expensive junk. > This is a lot. Actually this photo is a perfect illustration on how to create purple fringing or CA. The white is blown out and up against the dark foliage. Add to that the wide open f1.8 aperture and you get CA. Your 18-55mm kit lens probably would have taken the photo at f5.6. Admittedly this photo is a challenge. Experiment by exposing for the white so it isn't blown out then bring up the foliage in post. Also stop down the lens a bit in full sun. Modern Nikon cameras will minimize CA and processed in camera and viewed as a jpg or raw if using Capture NX2. I don't know if this is true in the D5100 but I expect it is.
The image will not be degraded as NX does non-destructive editing; the original is unchanged.
Purple fringing isn't a white balance issue, it's a lens issue. If you wanted to set up most any lens to fail in this department, over expose a bright area and set it in front of a dark background. Your 85mm is a good lens, not junk. Your 18-200mm isn't the greatest around and the 18-55mm is a inexpensive kit lens, although it performs quite well.
I edited your image in Lightroom to eliminate most of the purple fringing:
Thanks for the info. I only mentioned white balance as something that doesn't degrade the NEF image (as does sharpening). I see in your corrected version that the overexposed leaves still have it. I assume that means that you had to go after the offending line specifically rather than telling lightroom "get rid of the purple fringing". I guess that means that if one screws up in grand style while taking the picure, there's gonna be a lot of work in post production fixing the problem. Better to do it right to begin with .
This pic was just something I fired in my backyard just to see what 85MM looked like (since it is my first prime lens) with no real effort to get it right. But the purple fringing was just something I had never seen before and wasn't expecting.
I only adjusted the "Amount" slider in the "Lens Corrections" panel and was looking mostly at the white/dark borders. A little more time spent fine tuning things may have produced better results. There is still a light halo on the border, but at least it's not colored. How much is this image magnified? Too much pixel peeping can frustrate you!
Most of the editing you will need to do, including sharpening, doesn't really degrade the final image, it improves it, unless carried too far, of course.
Not sure how much it is magnified here. It was originally shot RAW at maximun size for a D5100 (4000+ x 3000+) and then cropped to fit the limitations of an attachment here. It appears to be the actual size as it appears when the full pic is displayed at 100% size (therefore requiring scrolling to see the various parts of the picture)