lovelifey: [Photography] Exposure in Photography: Everything You Need to Know

The post Exposure in Photography: Everything You Need to Know appeared first on Digital Photography School. It was authored by Darren Rowse.

What is exposure in photography? And how can you adjust your exposure settings to produce beautiful, detailed photos?

In this article, I’ll give you an exposure photography crash course. I’ll start with all the exposure basics, including fundamental terms like aperture, shutter speed, and ISO. Then I’ll share a few practical examples, which you can use to guide yourself when photographing landscapes, portraits, and more.

By the time you’ve finished, you’ll know how to carefully adjust your camera for perfect exposure results – and you’ll be well on your way to capturing stunning shots.

Let’s jump right in.

What is exposure in photography?

Exposure refers to the overall brightness of an image, which is determined by the amount of light that hits the camera sensor.

So by letting in lots of light, you’ll end up with a too-bright exposure (also known as overexposure), like this:

learning about exposure overexposed rose

And by letting in very little light, you’ll end up with a too-dark exposure (also known as underexposure), like this:

learning about exposure underexposed rose

But by adjusting your camera settings carefully – so you let in a perfect amount of light – you’ll end up with a shot that has plenty of details in the shadows (darks), the highlights (brights), and the midtones, like this:

learning about exposure well-exposed rose

Proper exposure is a fundamental goal in photography. Images that are poorly exposed tend to look bad and unnatural, plus they lose critical detail in the darker and lighter areas. That’s why, in order to take beautiful images, you must master exposure. Make sense?

The three elements of camera exposure

Exposure might seem complicated, but when you get down to it, it’s actually pretty simple. It consists of three camera settings that alter photo brightness; your goal, as the photographer, is to adjust the three settings so they are balanced.

In brief, these three exposure settings are:

Aperture: the size of the opening in the camera lens
Shutter speed: the length of time the shutter is open
ISO: the amplification, sometimes referred to as sensitivity, applied to the captured image

It is at the intersection of these three settings that an image’s exposure is determined. By adjusting any one element, you can brighten or darken the overall image, so you need to be aware of all three settings at all times.

(By the way, if you’ve ever heard the term exposure triangle, that’s what this is: three triangle corners that together determine the image exposure.)

Now let’s take a look at each element in turn, starting with:

Aperture

Every camera lens has an aperture, which is a hole – or diaphragm – in the lens barrel that widens and narrows depending on your camera settings.

The wider the aperture, the more light that goes through the lens and impacts the camera sensor, and the brighter the image.

Now, photographers refer to aperture sizes using f-stops, like this: f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc. A low f-number, such as f/2.8, gives a wide aperture, while a high f-number, such as f/16, gives a narrow aperture.

So when you’re taking a photo of a rose – like the example shot in the previous section – an f/2.8 aperture setting will create a brighter result (all else being equal). And an f/16 aperture setting will create a darker result (again, all else being equal).

Most cameras allow you to adjust the aperture via a dial on the camera top or rear, while others let you adjust the aperture directly on the lens. (If you’re not sure how to adjust the aperture on your camera model, check the manual.)

One more thing:

In addition to adjusting the exposure of your image, the aperture has another effect: It influences the amount of your photo that’s in focus, also known as the depth of field. Depth of field is completely independent of exposure, so I won’t go into the details now – but it’s important to know that, when you widen or narrow the aperture, you’re also changing the blurriness of your shot.

Shutter speed

Your camera has a shutter that blocks the sensor from receiving light. The second you hit the shutter button, however, the shutter opens, light hits the sensor, and a picture is created. Then the shutter covers the sensor back up.

The length of time from when the shutter opens to when the shutter closes is the shutter speed.

As you can probably guess, the longer the shutter speed, the more light that hits the sensor, and the brighter the image. An easy way to overexpose a photo is to set a lengthy shutter speed in bright light; you’ll quickly over-brighten (blow out) image highlights and ruin the shot.

Like aperture, you can adjust the shutter speed using a camera dial. Standard shutter speeds are fractions of a second, where 1/1000s to 1/8000s is considered fast, 1/250s to 1/1000s is considered average, and 1s to 1/250s is considered slow. (Once you go past 1s, you’ll be using a technique known as long exposure, and this isn’t advisable unless you have a sturdy tripod.)

Note that shutter speed doesn’t just affect image exposure; it also affects image sharpness, where a too-slow shutter speed will lead to blur, either due to camera shake or moving subjects. That’s why photographers use a tripod once the shutter speed drops below 1/100s or so (though the specifics depend on the lens, the camera, the steadiness of your hands, the subject, and even the weather).

ISO

An easy way to think of ISO is as the camera’s sensitivity to light. The higher the ISO, the more sensitive the sensor becomes, and the brighter the resulting shot.

Technically, this “sensitivity to light” explanation isn’t quite right – ISO is really a type of exposure amplification that’s added after the image is taken – but the details won’t affect your photos, and so I’d like to talk in terms of light sensitivity for now.

Most cameras have a base ISO of around 100. But as you boost the ISO to 200, 400, 800, even 25600, the exposure will get brighter and brighter.

Unfortunately, raising the ISO, while useful for increasing the exposure in certain situations, has an unpleasant side effect: it adds noise to your photos, which looks like little dots of light and color. This reduces image sharpness and quality, so it’s generally best to leave the ISO on its base value unless you absolutely need extra brightness.

If you do need to boost the ISO, however, look for an ISO button on your camera’s top display or in the camera menu.

Photo exposure: bringing it all together

Now that you’re familiar with the three elements of exposure, you can see how each camera setting cannot be considered in isolation. Instead, you must consider the aperture, the shutter speed, and the ISO when exposing your photos – because an adjustment of one setting will influence the overall exposure value and change the final result.

It’s also important to recognize that the proper exposure settings will vary from situation to situation. If the light is limited – for instance, if you’re shooting at night – you’ll need to widen the aperture, lower the shutter speed, and boost the ISO. Otherwise, your shot will end up pitch black. And if the light is very bright – for instance, if you’re shooting at noon on a sunny day – you’ll need to narrow the aperture, raise the shutter speed, and keep the ISO as low as possible.

Finally, remember that each exposure variable affects an additional aspect of your photos. Aperture influences the depth of field, shutter speed influences sharpness, and ISO influences noisiness. So when adjusting your exposure settings, you must think about exposure and these additional image quality and artistic considerations.

Determining the proper exposure in the field

I’ve explained how exposure theory works, but how do you set the exposure in practice? Are you supposed to guess at the settings until you get an image that you like?

Fortunately, thanks to modern camera technology, determining the right exposure value is pretty simple. Cameras are equipped with meters, which measure the light and indicate its brightness level. Your camera viewfinder displays an exposure bar, and as you adjust your three exposure settings, you’ll see the bar move toward the plus side (indicating overexposure) or the minus side (indicating underexposure). The goal, of course, is to get the bar to rest directly in the center of the bar, which indicates a perfect exposure.

In fact, modern camera technology makes things even easier than what I’ve just described. While you can set the aperture, shutter speed, and ISO individually – this is called Manual mode – you also have the option to shoot in Aperture Priority mode, where you set the aperture and ISO and your camera sets the shutter speed for a perfect exposure. Or you can shoot in Shutter Priority mode, where you set the shutter speed and ISO and your camera sets the aperture for a perfect exposure.

Finally, you have the option to shoot in Auto mode, where your camera selects the aperture, shutter speed, and ISO on its own.

(To choose a camera mode, simply adjust the Mode dial, generally found on the top of the camera.)

At this point, you’re probably wondering:

If cameras are so capable of determining exposure, how come it’s such an important concept to understand? Why can’t I just set my camera to Auto mode and forget everything I just learned?

For two reasons:

Sometimes, your camera’s meter gets it wrong. And in those cases, it’s important to know why the exposure is off and how you can fix it.
The exposure variables affect other aspects of your image, such as sharpness and depth of field. You need to know how adjusting each variable affects both exposure and image quality. Otherwise, you might end up with a photo that’s well exposed but that is annoyingly blurry, terribly noisy, etc.

That’s why I recommend you always set your camera to Aperture Priority mode, Shutter Priority mode, or Manual mode. These three modes guide you as you set the exposure, and they also give you the freedom to make adjustments when your camera gets it wrong.

Speaking of which:

Exposure mishaps: why your camera gets it wrong

Camera meters do a great job of determining the correct exposure value when faced with a neutral scene. They’ll make sure the scene balances out to a nice set of midtones.

However, some scenes aren’t meant to be neutral. Think about these situations:

A swan against a white sky
A snow-covered landscape
A white picket fence against a white house
A black cat at night
A dark car against dark pavement

In each of the above, your camera meter will try to expose the scene so you create midtones. It’ll darken the whites and brighten the blacks until it all becomes gray. And that’s not what you want.

Instead, you want properly white whites and properly black blacks. You want your dark car to look dark and your snowy hills to look bright.

So when you’re photographing scenes that are brighter than middle gray, you should deliberately overexpose the shot by widening the aperture, lengthening the shutter speed, or raising the ISO. If you’re shooting in Aperture or Shutter Priority mode, you’ll need to add something called positive exposure compensation, which basically just tells your camera to boost the exposure.

And when you’re photographing scenes that are darker than middle gray, you should deliberately underexpose by narrowing the aperture, increasing the shutter speed, etc. Alternatively, you might dial in negative exposure compensation to let your camera know that it should underexpose.

black cat on black requires underexposure

Usually, exposure correction involves adjusting by a few stops at the most (e.g., widening the aperture from f/8 to f/4), but I highly recommend you take several shots to be safe, especially when starting out.

How to expose for landscapes and portraits

In this section, I’ll give you a few pieces of practical exposure advice; that way, when you encounter specific situations in the field, you know what to do!

How to expose for an outdoor portrait

Say you’re photographing a person on a lawn. How do you select the right exposure variables?

First, I’d recommend setting your camera to either Manual mode or Aperture Priority mode. I’d suggest selecting a wide aperture, such as f/1.8 or f/2.8, so you can create an artfully blurred background (and to enhance the blur, move your subject away from any background elements).

Dial in a low ISO, such as 100, to prevent noise.

Then pick a shutter speed that will give you a balanced exposure. (If you’re shooting in Aperture Priority mode, your camera will do this for you!)

Once you’ve dialed in these settings, check your shutter speed. Is it fast enough to prevent blur? If you’re shooting on a bright day, the answer is undoubtedly yes, in which case you’re good to go.

However, if you’re shooting late in the evening or at night, your shutter speed might be too low (e.g., 1/30s). In that case, you’ll need to raise your shutter speed, then either widen your aperture farther or boost your ISO to compensate.

Take a test shot, adjust the variables as needed for a good exposure, and then start snapping away.

How to expose for a landscape

To create a detailed landscape shot, I’d recommend Manual mode, though Aperture Priority can also work well.

Set a narrow aperture, with the goal of keeping the entire scene in focus. You might try f/8 as a starting point, but depending on your results, you may need to push the aperture to f/11 or even f/16.

Set your ISO at its base level – probably 100 – so you can capture the best possible image quality. Then dial in your shutter speed based purely on exposure considerations. If the shutter speed is below 1/100s or so, you’ll probably want to use a tripod and a remote shutter release.

Finally, capture a test shot. Zoom in to check the depth of field, and make sure your exposure is bang on. If you’re shooting a sunrise or sunset, consider taking several shots – one exposing for the foreground and one exposing for the sky.

Exposure in photography: final words

Now that you’ve finished this article, you know all about exposure. You know how it works, how to adjust your camera settings for consistently great results, and even how to expose in a few practical scenarios.

All that’s left to do is get out and practice. Have fun working with the different exposure variables and experiment as much as possible!