Lesson 6. Master the Triangle

When I began to study photography, I learned it first as a technical craft, many years before ever truly beginning to learn it as an aesthetic one. Though the technical is important and forms the spine of our craft, what I should have been taught all along is that every decision I made also has aesthetic results and that those results are my choice. That choice gets easier when you’re comfortable with the give-and-take of the exposure triangle, because you’ll understand what you’re choosing and what you’re giving up with that choice in terms of the aesthetic of the image, regardless of whether you’re making JPG files or shooting in RAW. So, first, a basic lesson.

Light enters the camera, hits the film or sensor for a certain amount of time, and makes an image. Too much light and the resulting image is overexposed, if there’s an image at all on that white print. See? There really is too much of a good thing. Not enough light and your photograph will be underexposed, or completely black. Sometimes less is just less.

There are three basic ways to control how much light gets in. The first is to control the sensitivity of the sensor or film itself. With either medium you will choose an ISO, which is an international standard for light sensitivity. ISO 100 is “slow,” meaning much less light sensitive. ISO 3200 is “fast,” or much more light sensitive. The slower the ISO, the more light you’ll need to let in through the lens or shutter. The faster the ISO, the less light you’ll need, but the image will often get grainier, or noisier in digital capture, as a result. There’s a little give and take here, as there is with the other two points on the exposure triangle.

The second way to control the light is with the aperture in the lens, which is a diaphragm that opens and closes to control the light. It’s measured in cryptic little numbers that only mathematicians and practitioners of the occult understand. An aperture of f/1.8 is a very large opening despite its small number, whereas f/22 is a very small opening despite its large number. A large opening lets in more light, and a small opening lets in less. The side effect of this is that the tighter hole focuses the light much more than the larger hole. So letting in more light gives you much less focus from foreground to background. Letting in less light gives you more focus. Remember how I said there’s a give and take? This is part of it. Not only are we tasked with making a good exposure, but we also have to choose how we make that exposure because each choice has an aesthetic consequence. In this case, how we control the light with the aperture also controls the quality of focus.

Each setting has an aesthetic effect on the image. You can pick two; the third is where you compromise.

“The more natural this is to you, the easier it will be to make decisions when it matters. Few of us do our best creative work when we’re frustrated.”

The third way we can control light is with the shutter itself. In most cameras the shutter is like a curtain hiding the sensor from light until we press the shutter button. The shutter opens across the sensor for a specified amount of time, exposing the sensor to the light coming through the aperture in the lens. The give and take? Fast shutter speeds will freeze action because the sensor sees that action for such a brief fraction of time. 1/1000 of a second is pretty quick. Slower shutter speeds, like 1/15 of a second, can blur action because the shutter is open longer and sees more movement in that time, recording it as a blur.

That’s the exposure triangle. All three points on the triangle work together, and where you push the camera in one way, it will demand a little pull in another. If your first priority—because of what you want the photograph to look like—is a fast shutter speed (1/1000) to freeze action, then you will have to use either a much larger aperture (f/1.8) or, if you also want more depth of focus that using, say, f/8 would give you, then you’ll also need a higher ISO. It’s give and take. If numbers confuse you, as they do me, it’ll take a while before you’re comfortable, but you’ll get it.