Originally posted by jsherman999 Sigma 50 1.4: Made Nikon fanboys cry like little girls.
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I never had the pleasure of trying it out when I was with Nikon,since it was practically a new lens during that time and I was on my way out of Nikon's door. though would had loved to try it against the Nikon 50s.
I do somehow agree that the Sigma 50/1.4 has better overall rendering (sharpness, brightness and bokeh) than the Pentax 50/1.4. the Pentax is not that bad, actually it is even great or impressive by it's own right. the deal-breaker however leans more towards price and size, not the overall lens and IQ performance. Sigma is big/heavy and expensive. 2 of the 3 things that I don't like about the Sigma. and the 3rd reason is because I have a 1.2 which is awesome for portraiture.
for someone who is critical about IQ and doesn't have a fast 50 and who needs something for portraiture, doesn't mind lens size and has the money to spend, the Sigma would be the ideal choice.
for someone who is on a tight budget, the cheaper FA50 1.4 or 1.7 would be just as good. or buy some good old manual focus lenses for only $40 bucks.
an AF 85mm as you said would be just perfect for portraiture. so the Sigma 50/1.4 somehow loses ground there. and there's just too many 50's or near 50's jacking up for position.