As Chex said, it depends on lens and distance, which depend on the effect desired and the available space and light and background. Just for what I consider the right roundness for human features, I prefer around f/3.5-4 wiith a 75-80-85-90mm lens -- and that works for me in several formats, from APS-C | 135/HF to 135/FF to 645 to 6x6. For flatter features, use a longer lens from further away.
But I must balance these effects against the background: Is the BG near or far, soft or hard, lit or dim? Do I want to isolate the subject in full or part, or is the BG | context part of the portrait? What do I want to emphasize? The answers to these questions many lead me to use any lens from 50-200mm, at apertures from f/1.2-11, for facials. It all depends on what I want the portrait to portray.
Last edited by RioRico; 09-02-2011 at 01:40 AM.
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