Three-Minute Tech: Aperture and shutter controls

[In our Three-Minute Tech series, we tell you everything you really need to know about a technology in three minutes or less.]

In this world of filters, presets, and apps, anyone can tap a button and make a photo look like it was taken with a tilt-shift lens, captured by an old Russian camera, or painted with watercolors. But where's the fun in that? The downside to all that canned variation is that much of the creativity is handled by software rather than photographers.

If you have a camera with manual exposure controls, learning the basics of aperture and shutter adjustments can help you reclaim some of that creativity. This isn't an all-encompassing guide to aperture and shutter controls, but it should be enough to get you started.

Aperture and shutter

Aperture and shutter are the yin and yang of manual controls. Both settings have to do with adjusting how the image sensor is "seeing" your photo, but in different ways.

In very basic terms, setting the aperture defines how much light is hitting the sensor when the picture is taken. If your camera is an eyeball, the aperture is its pupil. Shooting with a very wide aperture is sort of like having your pupils dilated; it makes the sensor very sensitive to light, which comes with its own set of benefits and challenges.

On the other side of the equation, adjusting the shutter speed defines how long the sensor is recording the image coming through the lens. You're controlling time and condensing it into a single photographic moment! But when it comes to shutter speeds, "time" also translates to how much light is hitting the sensor, and that also presents its own set of challenges depending on the aperture setting you're using.

Aperture basics

When it comes to light-gathering abilities, aperture values are like golf scores: The lower, the better.

Aperture is measured in “F-stops,” with lower F-numbers translating to wider apertures. For example, an F2.0 lens is better equipped for low-light shooting than an F5.6 lens. Usually, you'll find wider apertures on lenses that don't zoom or have a limited zoom range.

A wider aperture lets you use faster shutter speeds, as the lens is doing some heavy lifting when it comes to gathering light. Lenses with lower F-stops are often referred to as “fast” lenses (i.e. you can use fast shutter speeds) or “bright” lenses (i.e. they gather a lot of light).

Wide apertures also translate to shallow depth of field. For example, if you dial in an aperture value of F2.0 and focus on a foreground subject, everything behind your focus point will likely be blurred out. If you take the same shot with a very narrow aperture, much of the background will be in focus. A wide aperture is great for portrait photos and product shots, where you want to isolate the subject from the background. A narrow aperture is better for landscape photography and wide-angle vistas.

Here's a shot taken at F3.5...

...and here's a shot taken at F22. Note the background details.

Shutter basics

Shutter speeds are more straight-forward. Faster, more commonly used speeds are represented as fractions of a second (1/100, 1/200, etc.), while slower shutter speeds are listed as seconds (1”, 1.5”, etc.). Slower shutter speeds capture more light--and blur--than faster shutter speeds.

If you don’t have a particularly “fast” or “bright” lens to work with, dialing in a slow shutter speed is a way to capture a sharp low-light shot. However, slow shutter speeds should only be used with a tripod or while resting the camera a flat surface. With a slow shutter speed, any movement—whether it’s the camera itself or objects in front of the camera--will show up as a ghostly blur.

With a slow shutter, static objects look really sharp, but anything in motion will be a blur.

Conversely, fast shutter speeds are only recommended with wide-aperture lenses or in very well-lit situations. If you use a fast shutter speed with an aperture setting that doesn’t gather enough light, you’ll end up with underexposed or pitch-black photos.

As you may have gathered by now, aperture and shutter settings are interdependent: Adjusting your aperture may involve tinkering with your shutter speed (and vice versa) to capture a well-exposed shot. And that's why aperture-priority and shutter-priority modes exist…

Aperture-priority mode

Aperture-priority mode, usually designated as "A" or “Av” on your camera’s mode dial, is the best entry point into manual controls. In this mode, your camera helps by meeting you halfway.

In aperture-priority mode, you just choose the F-stop. The camera picks the ideal shutter speed based on your input and the lighting conditions. It’s usually just that easy, but your camera can’t work miracles: Lighting conditions may be too bright or dark for the aperture value you’d like to use, and the camera will let you know by beeping, lighting up settings in red on the LCD screen, or displaying some kind of exposure warning.

"This photo is too important for me to allow you to jeopardize it."

If the camera indicates an image will be too bright, dial the aperture to a higher F-stop and try again. If the camera indicates the image will be too dark, dial the aperture to a lower F-stop and try again.

Shutter-priority mode

Shutter-priority mode is usually designated as "S" or “Tv” on your camera’s mode dial: You pick the shutter speed, and the camera selects an aperture value to properly expose the shot.

This is a handy mode for shooting fast-action photos and long-exposure shots, but again, your camera may refuse to cooperate. If the camera indicates that the photo will be over-exposed at your shutter-speed selection, pick a quicker speed. If the camera indicates that the photo will be under-exposed, use a slower speed (and possibly a tripod).

Manual mode

This is the open road when it comes to manual controls. You pick the aperture setting and the shutter speed independently. There’s a lot of room for experimentation, but there’s also a lot of room for error.

One tip for beginners is to use aperture-priority mode extensively, then check which shutter-speed settings the camera uses for the shots you like the most. This will give you baseline shutter speeds to work with when selecting aperture values, and you can experiment with slight adjustments from there. You can see shutter and aperture settings on your camera by pressing the “Display” button in playback mode or examining a photo’s EXIF data after the images are offloaded to a computer.

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