Thanks Rick. I hope one day to advance enough to use this info.
In the meantime I found a quote that was helpful to me too.
All the fancy technology in your camera (and some cameras list a lot of features) whirl and twirl… and eventually return just two values:
an aperture (how big a hole to open to let light in) and shutter speed (for how long to keep that hole open). ---
http://www.photoxels.com
