I took this picture the other day. It's a JPEG from the Fujifilm X-Pro1. The sky is overexposed as was necessary to light Anya brightly — and because I was playing with shooting wide open, and that plus the high base ISO plus max shutter of ¹⁄₄₀₀₀th meant this went beyond what the metering really wanted to do. Maybe a bit much, as we've lost the top corner of her head.
But, never mind that. What I'm interested in here is the cyan blur outlining the Prudential building in the background. A one-for-one pixel-level crop is below the full image....
Anya on the Esplanade; photo by me and CC-BY-SA 3.0 in this size only.
What is causing that blue outline? Is it just a matter of the out-of-focus blur interacting with the overexposed sky? Is chromatic aberration to blame? Or, is it because of the larger-than-normal color matrix used by this camera's unique sensor, and basically an artifact of RAW decoding?
Camera make : FUJIFILM Camera model : X-Pro1 Focal length : 35.0mm (35mm equivalent: 53mm) Exposure time: 0.0003 s (1/4000) Aperture : f/1.4 ISO equiv. : 200 Whitebalance : Auto Metering Mode: pattern Exposure : aperture priority (semi-auto)