The effects of light on the feathers? (1 Viewer)

Nearly forgot about this, re-found during an SD deletion exercise, shot almost a month ago in neighbour's garden. A blurred ''whoosh'' past the window and a hapless Song Thrush was snatched by this Sprawk. I took a short shutter burst, two out of focus and one in, deleted the former, retained the latter which is the subject shot, however the out of focus shots showed the normal tonal value.

I recall a BF thread perhaps a few months ago with a flight image of a Sprawk showing an ''apparent'' darker hood/head, which of course they don't have and it generated a bit of interest in as much as most people had not observed this phenomena...self included, especially as I often image sprawks.

I'm wondering if this is some sort of refraction at play, off the angled feather scales.....?

Very interesting indeed. I await the comments of the optics cognoscenti. . ..