When I first starting getting my feet wet in the world of photography it quickly became apparent that three settings on my camera COMPLETELY controlled the outcome of my image. There are other things involved (like background, focus... stuff like that) but understanding these three things is absolutely mandatory if you want to have a nicely lit, properly exposed picture. Shutter speed, ISO, and Aperture are the magic words. (Those attached articles are by a photographer who I don't know personally but I have a great amount of respect for, both personally and professionally. Go check them out!) The only way to control these things is to shoot in manual. So, buck up and go for it! I started shooting in manual right when I got my first camera. When the kids would play outside I would sit outside while they ran wildly and take pictures of things that WEREN'T moving... like my feet. Or a tree. Or a flower. When I would get a picture I liked I would try to figure out what I did right. I finally figured out that if I was properly exposed and then I changed something, like my shutter speed, the light coming into my camera changed. So, if I changed my shutter speed to catch an action shot, for example, I would have to compensate by changing either my aperture or my ISO.
Over the next few weeks I will be posting how to control each of these three parts of the pgotography triangle and what difference (aside from light) they will make to your picture. For now, the thing you need to remember is that each of these three things will either let more light in or keep light out depending on how you adjust them. And light, my friends, is the number one thing you MUST understand to get a true understanding of photography.