What you’ll learn from this article:

• what each of the A (Av), S (Tv) and M modes are, a definition of each
• what types of situations I would choose each of them and why
• some advantages of A (Av) and S (Tv) over manual
• some advantages of Manual and when it’s the only choice
• some things to look out for http://digital-photography-school.com/getting-off-auto-manual-aperture-and-shutter-priority-modes-explained