Okay, vocabulary lesson is over, and hopefully you have the terms shutter speed, aperture, and ISO burned into your minds. And, hopefully, you got your camera off of Auto, did some reading, and can now come pretty close to getting a good exposure by setting things manually. It’s not that you have to set things manually; but you should know how in case you want to.
I mentioned last time that, if you change shutter speed, aperture, or ISO, your exposure will remain the same, but the image will change slightly. Let’s look at how, and how you can use the three factors of the exposure triangle to add diversity to your images.
Aperture: This is the one that, when people learn about it, they slap their foreheads and groan. To a certain extent, control over aperture is the most important way to learn to control your camera, because it will influence how much of an image is in focus.
Let’s say you have a 50mm f/1.8 lens (which is lens you should have, by the way. Dirt cheap and excellent), and you set the aperture at f/1.8. This is called “shooting wide open”, because the aperture is as big as the lens will allow. The effect, especially if you are close to your subject, is to render some of the image in sharp focus, while throwing the rest into a blur. Your image has a “shallow depth of field.” This is particularly popular in portrait and wedding photography, where a subject might need to be separated from a distracting background.
Alternatively, let’s say you have your lens at f/16. This is called “stopped down”, because your aperture is closed way down. The effect is that almost all of your image will be in focus. Your image has “great depth of field.” This is particularly popular in photojournalism, street, documentary, and landscape photography, where the context in which an action is taking place, or the location a subject is in, is considered to also be an integral part of an image. In fact, rule #1 in photojournalism is “f/8 and be there”, meaning that it is most important to be present for the action and to capture an in-focus shot; other artistic and stylistic concerns are secondary at best.
Very often, you will want to shoot somewhere in between. Turn your camera to “P”, which is “program” mode. As you take a picture, take note of the settings the camera chooses. It will probably favor an f/stop such as f/5.6-f/11. This is a good model to follow for general photography.
Shutter Speed: We want our image to be in focus, but we also want them to be “sharp”. That is, there should be little to no blur resulting from motion in our images, unless we want it to be there for a specific effect. This is where shutter speed becomes important.
No matter how little coffee you have consumed today, your hands still shake and your body still sways a bit as you take a picture. Shake and sway enough, and you will ruin the shot. But if you shoot with the right shutter speed, the shaking and swaying won’t be seen. There is a rule that the slowest shutter speed that is safe is the inverse of your lens’ focal length. So if you are shooting with a 50mm lens, do not let your shutter speed go slower than 1/50 of a second. If you are shooting with an 85mm lens, then no slower than 1/85. A 200mm lens? 1/200 is the safe limit.
The above image was shot with a 1/500 shutter speed…fairly fast, and enough to freeze the action. But if you want to convey a sense of motion, you might want to shoot with a slower shutter speed to create blur deliberately. Sports photographers do this all the time when they are not freezing basketball players mid-dunk. Do you have a small child who is always running around? Do you want to capture that movement? Setting a slower shutter speed is how you do it.
And why not push it really far? With a tripod, a plan, and some practice, you can use motion blur to create ethereal effects in your imagery. I’m sure you have seen pictures of a wooded waterfall where the water is transformed into these gossamer silken ribbons falling over and around rocks. That is shutter speed used creatively. Give it a try.
ISO: sensitivity will not have a direct effect on what the image looks like in the same way that aperture and shutter speed will. Instead, ISO affects how much noise or grain is in your image. The higher your ISO, the higher the amount of digital noise or film grain that you will see, and for most purposes, that is bad. You want to keep your ISO as low as you can if you want clean-looking pictures.
That being said, current digital cameras can shoot cleanly at ISO3200 and above, and that really is a marvel, especially for photography indoors. I am always amazed by how little light there actually is indoors even when it looks bright, and also by how much light there actually is outdoors even when it looks dark.
In bright sunlight, ISO 100 is perfect. Indoors in window light, ISO 400 or 800. Indoors but not directly in window light, ISO 800 or 1600. You can even photograph someone blowing out birthday candles fairly easily between 1600 and 3200.
Homework: Three parts! Put your camera on “A” or Aperture Priority, and shoot some wide open, some with middle apertures, and some stopped way down. Then, put your camera on “S” or “Tv”, for Shutter Priority or Time Value, and shoot with fast shutter speeds and slow shutter speeds. Try to find something in motion, and practice freezing it, as well as trying to capture some blur. And shoot some outdoors and a few different locations and times of day indoors, and adjust your ISO so that you can have the aperture and shutter speed you want. You turned your flash off, right?