The Basics: Aperture, Shutter Speed & ISO

What is aperture?

The opening in the lens that restricts the amount of light that can enter it is referred to as the aperture. By changing the aperture, you can either increase or decrease the size of that opening, which allows more or less light into the camera.

The f-stops, such as f/16 and f/4, are used to measure aperture. The lower the f-stop number, the bigger the opening, as well as the other way around. When you adjust the settings, consider the opposite: Choose a larger f-stop if you want less light to enter (small aperture). How large your focal point’s opening can open will rely upon your focal point.  Note: The model name of your lens will include its maximum aperture (such as a 50mm f/1.8 or a 24-120mm f/4.)

Aperture is responsible for determining an image’s depth of field (DOF), in addition to controlling light levels. The depth of field, or DOF, is the amount of depth that will be in focus in an image. The focus will be sharp from the foreground to the background in an image with a large DOF, whereas in an image with a small DOF, or shallow DOF, the focus will be on a single plane and the elements of the foreground and background will be blurred away.

Choose a smaller number (larger aperture) for a shallower depth of field (DOF) or a larger number (smaller aperture) for a wider DOF.

When would you require aperture control?  Almost always. Portraits and landscapes are the most common types of photos that require aperture control. With a shallow depth of field (DOF), portraits often look better when the subject is separated from the background.

With landscape photos, we typically want everything in sharp focus from the foreground foliage to the distant mountains. The beauty of digital photography is the ability to “guess and check” when determining depth of field. To achieve the desired DOF, simply take a picture, examine it on the LCD screen of the camera, and either increase or decrease the size of the aperture.


What is shutter speed?

A camera’s shutter opens to let light in, just like a window’s shutters do. The shutter speed is the amount of time it stays open, like 1/60 of a second. The shutter is located directly in front of the imaging sensor.

The shutter speed and aperture work together. The shutter controls the amount of time the sensor will be exposed to light, whereas the aperture controls the amount of light entering the lens. When you set the shutter speed, which is typically expressed in fractions of a second (e.g., 1/30, 1/1,000), you are instructing the camera to open and close the shutter quickly or slowly. A shutter speed of 1/4,000 second is very fast and lets very little light in, whereas a shutter speed of 1/2 second lets a lot in.

The camera’s motion is captured by the shutter speed in addition to its role in exposure. A slow shutter speed will record the movement and allow objects to blur, while a fast shutter speed will freeze moving objects in their tracks. Even though you need a certain shutter speed to take a steady picture without a tripod, blur and sharpness aren’t always bad. There are numerous instances in which choosing between the two is creative rather than technical.

Take, for instance, a race car: Some people might want to show how it moves around the track with a blurry effect, while others might want to freeze it to show a specific moment, like when it crosses the finish line. In the first example, you should try using a slower shutter speed like 1/60, while the second one would require a shutter speed of at least 1/1,000.

A few things should be kept in mind. To prevent camera shake, ensure that your camera is stabilized on a tripod or other steady surface when using a very slow shutter speed. The focal length of your lens and whether or not it (or your camera) has image stabilization are two of the many factors that influence the slowest shutter speed that you can shoot at while holding your camera in your hand without introducing shake. For handheld shots, shutter speeds of 1/60 to 1/125 seconds (or faster) are generally safe.


What is ISO?

The International Organization for Standardization is shortened to ISO, but its significance in photography is distinct. A rating from the days of film that still applies to digital cameras but is also referred to as “film speed.” The sensor’s response to light from the shutter and aperture is controlled by ISO. An image with a high ISO is brighter, while one with a low ISO will be darker.

While ISO, aperture, and shutter speed all have similar effects on exposure, the first two have creative side effects like DOF and motion blur. In general, you should keep the ISO as low as you can while still getting the right exposure, as increasing the ISO also makes noise worse. When someone says that a photo is “too noisy,” ISO is probably to blame. We rarely want noise to have a creative effect, and if we do, it’s usually best to add it in post.

Color depth and dynamic range are also better recorded by sensors at low ISO settings. High ISO films were once “grainier” in appearance. Noise and grain can be considered to be one and the same thing.)

The ISO can be set to a low value, typically between 100 and 400, in scenes that are well lit or in daylight. In such situations, you typically only need to adjust the aperture and shutter speed to get the right exposure. In any case, in faint lighting, there might be no other choice than to expand ISO. Also, if you want a fast shutter speed and a deep depth of field with a small aperture, you might need to increase the ISO.

In contrast to shutter speed, ISO is represented by a number that does not correspond to any actual measurement. The majority of cameras can be set to ISO 12,800 or higher from 100 or 200. Fortunately, the math is simple: The brightness is doubled when the ISO is increased, so ISO 800 is twice as bright as ISO 400, which is twice as bright as ISO 200, and so on.

There are a lot of cameras that claim to have insanely high maximum ISOs, but don’t always believe what they say. You shouldn’t use a camera just because it can shoot at ISO 102,400.


How do these three work together?

Aperture, shutter speed, and ISO all work together to properly expose an image, as you probably concluded. The other two will be affected by any change to one. To maintain the same exposure value, for instance, increasing the shutter speed must be accompanied by an increase in ISO or aperture size. Diminishing the size of the gap (choosing a bigger f-number) will require a quicker shade speed or lower ISO.

To put it another way, choosing an exposure will always necessitate some level of compromise. In most cases, you will be able to choose the exact settings you want, but it might be hard to find a balance that gives you the DOF, sharpness, and noise levels you want in tricky lighting setups.

You might want to try a compromise between fully automatic and fully manual exposure modes if this all seems a little too complicated. While still allowing you some degree of control, this middle ground method streamlines and simplifies the exposure process. You can control the depth of field by setting the aperture in Aperture Priority (A) or Aperture Value (Av) mode. However, you don’t have to worry about setting the shutter speed because the camera will take care of that for you. On the other hand, Shutter Priority or Time Value (S or Tv) can be used to manually select a shutter speed, and the camera controls the aperture. Auto ISO typically operates without regard to the mode of exposure. Although turning it on might cause more noise, doing so will make the process even simpler.

If you are new to it, all of this may seem like a lot, but keep in mind that there is no magic formula for getting the most exposure. Don’t take it personally if you have to change your settings during a shoot to get the best composition, as professional photographers do. Experiment and have fun are the most important things.

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