50mm are pretty good prime lenses, especially for portrait style pics. The two lenses are similar but the macro has a closer focusing distance hence making macro (1:1 magnification) possible. The macro is also slower at 2.5 vs 1.8 which won't really matter for macro as in most cases you'll want more DOF but it will lack some of the ability to minimize DOF and increase shutter that you sometimes want with a portrait lens. So although similar they are geared towards different things. Personally I think a 50mm is too small for a macro and you'll find yourself having to get too very close to the subject for a real macro. You really need two lenses, the 50mm 1.8 (or 1.4 even better) and the 100mm macro.
Last edited by sphelps; 02-20-2012 at 02:43 PM.
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