Just a Glimpse

I was going to blip the photo looking down over the gorse from above Stephens Bay, but decided to use another looking up instead of down, because I am curious and hope someone has an answer for me. The rejected photo is in the extras.

Can anyone tell me why there is a pale sort of halo around the edges of the foliage framing the distant sea and mountains? I thought at first it may be over sharpened so I took all sharpening out but it made no difference at all.