"is academic question, and you will never "set" a rule for it. Many times, after Carravagio, there was attempt to teach through set of roles, especially in England where art was at its "high"."
i was not trying to make a rule, I only noticed that I tend to do things a certain way. I had wondered if anyone else did the same and if it can stem from certain psycological or psyiological (sp?) qualities.