Oh come off it Mr. "I just want to argue to show everyone how smart I am but screwed it up." If some one spouted that they had an "F 0.5 lens", they would just be showing that they were an ignorant ass - oh, wait, maybe that's you! First of all, by convention it's "f/" not "F". Note the "/". We may say, "eff eight", but we only do so because saying "eff divided by eight" is just to God damned many syllables. Further, 1:2 and 1/2 are ALWAYS unitless ratios expressing aperture over the focal length, whereas f/2 is ALWAYS an actual aperture size measured in linear units (a = f/2). If the focal length (f) is 50 mm, then f/2 means the aperture is 25 mm. If the marking is 1/2 or 1:2, then this is ALWAYS the ratio of the aperture to the focal length. Summing it up, f/2, 1/2 and 1:2 all mean the same thing. F 0.5 or f 0.5 is some kind of nonsense unless you're trying to make up some convention of your own. Some lenses are actually marked 1/2.8, 1/3.5 etc. Regards, Bob.... -------------------------------------------------------------------- "Beer is proof that God loves us and wants us to be happy!" - Benjamin Franklin From: "Steve Hodges" <shodges@iinet.net.au> > Bob Blakely wrote: > > > > It's the same as 1/ (for all practical purposes). > > > > 1/2.8 would be more universally recognized, wouldn't it. > > :-) > > No, because someone with a lens marked 1/2 would start sprouting that > they had an F 0.5 lens.
