What is the difference between an amateur and professional.
A very important question for everyone, every day.
When I started to think about it, I wanted to find a simple, fast-acting formula.
The professional thinks: HOW IT WORKS,
and
An amateur thinks: WHAT TO DO.
Easy to distinguish.

later, in one forum I found:
1.   Amateurs worry about equipment ;
2.   Profesionals worry about money ;
3.   Masters worry about light ;