A reader asks:

“Question: I understand why you would use most of the modes ( av, tv, etc.) but what are the main applications where one would/should use the manual mode? Thks”

Great question.Why use manual? Here’s why you want to use manual (“M”) exposure mode (the dial on top of your camera).

• Predictability. If you set the camera to manual exposure mode, your settings are, well, set. Turning your camera a little to the right or left will not now change your exposure. Imaging you are shooting in a room with predictable light, but your subjects walk in wearing white suits, then black suits, then white suits again.
• Hard to measure subjects. How are you going to measure fireworks? It cannot be done in any automatic mode since when the metering is done, it’s all over.

That means you will want to use manual exposure mode in the following circumstamces:

• Whenever using indoor flash. See http://blog.michaelwillems.ca/2010/03/18/reader-question-2/
• Whenever shooting indoor sports.
• In any studio or studio-like situation, i.e. when using manual flashes or continuous lights.
• At night, when doing night shots.
• When doing long exposure shots.

Some photographers say “always, and use a meter”, but for me, the above captures it nicely.

PS: be careful: there are many types of manual. See here: http://blog.michaelwillems.ca/2010/03/11/manual/