No lens is optically perfect. In the ideal world, every lens would produce a sharp, undistorted, evenly illuminated image that’s sharp from edge to edge. Some lenses come close, but the fact is that lens designers have to work within the limitations of the laws of physics and the glass materials they have available, and […]
Axial chromatic aberration
Axial chromatic aberration is colour fringing that appears around out of focus objects. It happens when the lens defocuses different colours differently, e.g. blue goes out of focus more quickly than other colours and creates a soft blue fringe round out of focus objects.