Blue hour at the Golden Bridge, Inverness Campus. Temperature falling rapidly, so a chilly cycle home.

Have noticed that skies like the above have steps in the blue colour rather than a smooth gradient. Suspect it's something to do with it being a JPG file, as it's not obvious in the original RAW version. Camera? Something else to keeping a watch for the occurrence of, or more likely,  I'm just being overly fussy... again.