Chromatic aberration, or colour bleeding as it is commonly known, is a flaw, usually in the form of a coloured halo and inhibited focus, in the composition due to the lens. Different wavelengths, or colours, of light focus and magnify slightly differently, and without special glass elements with the lens called low dispersion glass (ED in Nikon lenses, UD in canon), this problem can occur. Lenses that contain such elements are called apochromatic.

However, it need not always be a problem. In this photograph, there is significant colour bleeding; however, I do not see it as a flaw that subtracts from the photograph, but rather adds to it. As Laurie Simmons commented in her interview with Llana Stanger, "There's a lot I do wrong that I think enhances what I do".

I took this on an overcast day with Fuji Sensia 400 ISO slide film, 1/125, f/4 using my 135mm Nikon lens with a +1 dioptics Vivitar close-up lens. These are old lenses, and so not equipped with the same preventative glass elements as modern lenses are. In combination with the type of film, the presence of other cow vetch flowers blurred in the background of the subject, and my use of an 81b cooling filter mounted on my cokin filter system, the result is the soft colour bleeding you see in the photograph.

For more information on colour bleeding, visit http://photonotes.org/cgi-bin/entry.pl?id=Chromaticaberration.