In article <41142t$9pa@news.iastate.edu>, tosak@iastate.edu says...
>I would appreciate if someone can explain to me what is flat field in >macro lens, e.g., Nikkor 60mm AF-D Macro lens? How does it work? And >if lens that does not have it, i.e. flat field, e.g., Nikkor 105mm AF-D >Macro lens, what will affect the picture on film?

Do not worry - all the Nikkor macros are flat-field in the close-up
range (the 55mm f3.5 is the only one in which I have observed field-curvature [mostly near infinity focus]). Flat-field means just that: able to render on film (which we trust is flat, but it isn't
always flat, alas) a flat image of a flat subject. Failure of a lens
to do that means that a flat subject (like a drawing, or the horizon)
cannot be focused center-to-corner in the image at the same focus
distance setting on the lens (assuming the film and subject planes
are parallel). Hope this helps.