Zip Doodah said:
What does 'CA' mean?
Chromatic aberration is color fringing caused by photography. Different light frequencies "bend" through the lens at miniscule different angles (coated-lenses attempt to minimize this effect):
As shown in the diagram, the capture-lens focus is thereby imprecise across the R-G-B color slices that compose the complete picture:
Colors slightly out-of-focus are slightly different sized from the one color in-focus. Because the capture lens always is axis centered, simple resizing (which is also axis centered) keeps picture alignment the same. However, for this Song Of The South frame, the axis was at the bottom left corner (!) indicating the frame had been previously misaligned. Enlarging only the Red separation by a pixel or two (height & width) and shifting from the bottom left corner (instead of center-picture) did a good job correcting the problem:
