Aperture, the size of the hole letting light through your lens, is the third variable you control to get properly exposed photos. Last October I discussed ISO, the sensitivity of your camera’s digital sensor. In November I wrote about shutter speed and how your choice is a creative one as well as an exposure control.
Like shutter speed, the aperture you choose affects the “look” of your photo as well as the exposure so it’s both a creative and technical choice. The family portrait above was made at a middle aperture to balance depth of field and shutter speed with proper exposure.
You can think of the aperture as the size of the “light pipe” carrying photons through your lens. The larger the diameter of the pipe, the more photons go through, just as a 2” water pipe carries more than a ½” pipe. Continue reading →
Last month I introduced the three things you can control on your camera that affect exposure: ISO, shutter speed, and aperture. I explained how changing the ISO setting changes the sensitivity of your camera’s sensor. If you missed it, or need a review, read about ISO here.
Shutter speed is this month’s topic. Choosing an appropriate shutter speed for your subject is a creative choice as well as being one of the variables that affect exposure. All cameras have a hole inside the lens that, when open, lets light hit the sensor (or film). The shutter controls how long the hole is open.
When the shutter is open for a very short time you are able to stop motion and freeze action. Conversely, a long exposure can blur a moving subject. If you’re hand-holding your camera you need to choose a shutter speed that is short enough to compensate for any movement of the camera in your hands. The longer the focal length of your lens the shorter the shutter speed needs to be to avoid camera shake.
When you go to the beach do you want a sunburn, a nice healthy tan, or a pale complexion? You’re in control by how much you expose your skin to the sun. If I spend too much time outside without my hat, my balding head gets burned. That’s analogous to an over-exposed photograph, although the results usually aren’t so painful.
This month and the next few I’m going to help you make sense of the three variables that interact to affect photographic exposure: the sensitivity of the digital sensor (or film), how long the light strikes the sensor, and how big is the hole the light passes through. We call those the ISO, shutter speed, and aperture. I’ll get to each of those and how they interact in this and the next few installments, along with exposure compensation.
You may wonder why this is important if you always use your camera in its fully automatic mode. In full auto, your camera is measuring the light and setting the ISO, shutter, and aperture to expose the subject correctly. Taking control yourself gives you creative options you don’t have in full auto mode.