So the last thing I posted about was ISO right? So for today let's talk about how aperture and shutter speed work together to give you a proper exposure. A proper exposure is basically when you have colors from solid whites to solid blacks in the photo. Lots of times though it's an artistic decision. An overexposed (too bright) photo may be more artistically pleasing than if it were technically exposed correctly. So in the end, learn how to get a proper exposure and then experiment.
I usually leave my camera set on an ISO of 200 so for now let's just look at how shutter speed and aperture work together and then next we'll worry about how ISO affects (or is it effects) all of it.
First you need to know your camera's metering system and what to set it on. I know reading the manual isn't fun and a lot of times looks like Greek, but it's just necessary. So find the section in your manual about metering modes, grab your camera and start learning. For example on mine there are different metering modes that could affect how my camera reads the scene. So it's important you get out that manual and figure out exactly how your camera meters and the different metering modes.
Now the next thing you have to figure out is how to read it in your viewfinder. Usually it looks something like this one below. On my digital SLRs (and I'm assuming on most) you'll see one in the viewfinder as well as on the LCD screen.
Basically you want that little mark on the bottom to be in the center. But there are other things to consider. Do you want your background blurred more? Do you want to freeze motion or blur the motion. For me it depends on the situation. If I'm photographing children for a session I usually want my aperture lower so that the background is more blurred. If it's my son playing basketball or golf I want to freeze the motion so I want a faster shutter speed.
For example if a shutter speed of 200 and aperture of 5.0 would give me a proper exposure, but I wanted a more blurred background so for every stop down I moved my aperture, I would increase my shutter speed until my mark was in the center. Basically, if you move one down you need to move the other up and vice versa. Have I thoroughly confused you? It's one of those things that for me I had to just practice and it finally clicked.
Now a little tip. It's best to meter off what ever you want your subject to be. For example I usually want the child I'm photographing to be properly exposed. So I get in close and meter off the child's face and then leave the camera on those settings. Then I step back, recompose the shot ignoring what the camera's meter is trying to tell me leaving it on the previous settings.
So here are some photos that will hopefully illustrate how the shutter speed and aperture work together. The settings were different, but they all gave me a proper exposure.
This first one I used a larger aperture and faster shutter speed. f/3.2, SS – 1/1600, ISO 200
In this second one I changed it to the following: f/5.6, SS – 1/640, ISO 200
And the settings on this final one: f/11.0, 1/125, ISO 200. The slower shutter speed blurred the motion of his swing as well as missing the ball, but the narrower aperture brought more of the background in focus.