How can I take photos using a mac KB? F11 is my volume control so it won't take the pics.

On Mac keyboard layouts, F13 = Print Screen.

Of course, that's not of much help if you're on a laptop...but the desktop boards are pretty much the same as Windows ones save for a couple of keys swapping positions and a bunch of the keys being renamed.

If you're on a macbook laptop, you can press the Fn key and the desired function key (so, fn + F11).

By far the easiest way to do it would be to go to System Preferences > Keyboard and check "Use all F1, F2, etc. keys as standard function keys", under the Keyboard tab.