FoPP 010 1.II.2.Finger Positions
Fundamentals of Piano Practice - A podcast by Chuang C. Chang / Henrik Pantle

Everyone seems to have her/is own ideas about finger positions, so it is clear that there are no rigid rules. The only guidance is that the fingers should be in the most relaxed and powerful positions... http://www.pianofundamentals.com/book/en/1.II.2