Exposure Definition Photography: Aperture, ISO and Shutter Speed

Photoshop Effects

What is exposure definition in photography?

The exposure of a photo is what makes a photo lighter or darker once it’s developed or in hard copy. It sounds like a complex concept, but it isn’t once you understand it.

The Exposure Triangle

You control exposure with three settings on your camera:

  • Aperture setting
  • ISO setting
  • Speed

Photographers call this the “exposure triangle.” These three settings work together to give you the desired effect of your photo. It might be the final product or it will give you something from which to edit to get the perfect result.

Knowing how to use these three settings on your camera and the effect each will have on your photos allows you to hone your photography skills.

Taking a Photo

Let’s begin with how a photo is created.

When you’re taking a picture, you aim your camera, press the shutter button, and whatever you are shooting “enters” your camera in light form.

When the subject is amply lit, there is a lot of light that travels into the camera, but if you’re working in a darker setting less light enters with the image.

The light entering the camera passes through the aperture and then reaches the “window” or shutter. The length of time the shutter is open determines how much light seeps in with the image. This length of time is called the shutter speed.

EA slower shutter speed allows more light and a faster shutter speed allows less light in. The ISO then brightens darker images.

Finally, the shutter closes and prevents any further light from reaching the camera’s sensor.

To summarize how each of the three components works:

closeup camera exposure adjustment control

Aperture controls the mechanism allowing light to enter your camera.

Shutter speed controls the length of the exposure.

ISO speed controls the sensitivity to certain amounts of light.

By using these three settings in different combinations, you achieve different effects. The key to good photography is knowing how to make these adjustments and blend the settings “just so.”

What Do You Need to Know about Shutter Speed?

Shutter Speed Characteristic Examples:

  • Use 1 – 30+ seconds for night and low-light photos
  • Use 2 – 1/2 seconds to create a soft, dreamy look to flowing water
  • Use 1/2 – 1/30 seconds to add soft blurriness behind a moving subject
  • Use 1/250 – 1/500 seconds to freeze a sport/action subject’s movement
  • Use 1/1000 – 1/4000 second to freeze an extremely fast, close range subject motion

So let’s look at a few examples of how you would adjust your settings in different situations.

Consider how much you want to blur based on the movement of the object. For example, you’d shoot a waterfall different from a bowl of fruit. You’d use different settings photographing someone running a race than you would someone dancing ballet.

The goal is always to get the sharpest photo possible, but you aren’t going to be capturing an image moving or not moving in exactly the same manner every time.

Ideally, you’ll figure out how to get the crispest photos by experimenting with the settings on your camera and get to know what works. The great thing about shooting digitally is that this is much easier to do because you don’t need to wait hours for the photos to develop.

Still, you want to practice as much as possible because you don’t want to miss out on capturing a special moment that was gone in the blink of an eye.

Working with the Aperture

closeup of camera lens aperture

Next, you’ll want to experiment with the aperture.

The aperture diameter controls how light passes through the camera lens. You measure it via an f-stop value.

What confuses a lot of novice photographers is the fact that as the size of the opening gets bigger as the f-stop value gets smaller.

It’s the reason some veteran photographers use terms like “stopping down” or “opening up” when referring to f-stop value. A narrow aperture means larger f-stop value, and a large aperture means a smaller f-stop value.

Every time the f-stop value decreases by half, the light-intake space quadruples. You can use a formula to remember this, but there’s another trick that most photographers find easier to remember.

If you know the f-stop numbers that correspond to the doubling/halving of light it’s easier to figure out what you need.

Here’s a handy chart:

Aperture Setting         

  • f/22      1X        16 seconds
  • f/16      2X        8 seconds
  • f/11      4X        4 seconds
  • f/8.0     8X        2 seconds
  • f/5.6     16X      1 second
  • f/4.0     32X      1/2 second
  • f/2.8     64X      1/4 second
  • f/2.0     128X    1/8 second
  • f/1.4     256X    1/15 second

So, in summary, aperture determines a photo’s depth of field. This is the how far of a range objects can come into sharp focus. The lower the f-stop value the shallower the depth of field.

Understanding ISO Speed

camera lens view iso setting

Finally, we’ll take a look at the ISO speed. ISO speed controls how sensitive the camera is to the light entering it. It interacts on a 1:1 ration regarding increase and decrease.

However, in most cases, a low ISO speed is preferred because it reduces image noise.

The ISO speed controls the camera’s sensitivity to light coming into it. Comparable to shutter speed, it also interacts 1:1 with how much the exposure increases or decreases.

But different from the first two settings, a lower ISO speed is usually desirable, since a higher ISO speed can increase brightness information, also known as image noise.

The most commonly used ISO speeds include:

  • 100
  • 200
  • 400
  • 800

This is something some people might remember from back in the days when shooting with a film camera was the only option. You could buy film in various speeds, including the numbers listed above, and some might be labeled for “high action” or “sports” based on the types of images they were most capable of capturing.

It takes practice and experimentation with your camera to get to know and be comfortable with the settings and what you’re able to do with those settings.

But once you understand the exposure definition in photography taking great photos will come easier to you. The important thing is to not worry too much, especially at the beginning, about messing anything up.

The goal is to get to know how things work from a hands-on approach, and eventually you’ll improve your photography skills.

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