The last of the three important factors in proper image exposure is the easiest to understand: shutter speed. The shutter speed determines how long the sensor (or film) is exposed to light. The camera has a shutter between the lens and sensor which opens and closes for a time period determined by the shutter speed setting. Shutter speeds are typically expressed in fractions of seconds, so if you see 125 in your viewfinder, your shutter will be open for 1/125 of a second. The camera does this for you when you are in the program mode, but, remember our goal here – you are going to take control of the camera! To keep your images sharp, keep the shutter speed above 1/30 unless you are using some kind of support like a tripod. With practice, you will be able to hand-hold at lower shutter speeds, but you should use the highest speed that meets the requirements for your situation. I know you probably have vibration reduction in your new camera, but it is reduction, not elimination.
So we just set our cameras to lightning fast speeds, and we can stop the action on fast subjects – even water droplets, race cars, or the Air Force Thunderbird F-16s, right? When do we need to take control of the speed setting? Ideally, you are thinking about how you want the final image to look; so, if that image should show some kind of motion, you’re going to need to adjust the speed. There are other reasons, but this is the most common, and we’re keeping it simple right now. Here are three examples of showing motion. The rider is moving at a gallop to pop the balloons. The racing bike riders should look like they’re moving. And when a little kid hits the slide, you want your image to capture the motion that excites her.
So, if you have read the last three blog entries, Mark and I have given you the basics of the big three for exposure (aperture, ISO, shutter speed). You should be able to think through an image and understand the importance of controlling your camera settings and why you want to move away from the program mode. When you put it all together, you can get the picture you want.
We’ll go into more of this in deeper detail down the road. There are many reason to change thes exposure settings and nuances with which to become acquainted as you progress towards total image control. Feel free to leave comments and ask questions. The more you practice, the easier it is to take control and understand how to make the camera do what you want. Get out there and play around until you are comfortable with these basics. Have fun with that camera control.