What is Good Exposure in Photography?
July 2, 2018 Production Skill Tips & Tricks
If you’re trying to get into photography, one thing you’ll hear often is to make sure you’re getting good exposure. What exactly does this mean? To really make sure you’re getting a photo with good exposure, you’re balancing out three major elements; ISO, shutter speed and aperture. Every time you adjust one, you will almost certainly need to adjust another. By understanding how to work with these three components on your camera, you will be able to see why your photos are underexposed or overexposed.
Let’s start with aperture.
Aperture is essentially the opening in the lens that allows light in. The larger the hole, the more light is allowed in. Aperture is measured through ‘f-stops’. Adjusting from one f-stop to the next will either double the size of the opening, or shrink it in half. Most modern lenses use a standard f-stop scale—f/1.8, f/3.5, f/5.6, f/8, f/16 are some common f-stops you may see. Although you may think it should work in the reverse, as the f-stop number goes up, the lens opening shrinks, and vice versa. For instance, an f-stop of f/2.8 is going to have a much larger aperture than f/22, thus bringing in more light.
The aperture also effects the depth of field of your image. Think of a portrait shot vs a landscape shot. In the portrait shot, you would usually want the persons face in focus, while the background is out of focus and less of a distraction. Whereas with a landscape shot, you want everything in focus—the foreground and background. A wider aperture (f/2.8) will decrease the depth of field and create a blurry background, while a smaller aperture (f/22) will increase the depth of field and bring everything into focus.
Now tie this in to shutter speed.
Shutter speed is the speed at which your shutter is opening and closing. In other words, it’s the length of time that your shutter is open, allowing light into your camera before it snaps closed again. Fast shutter speeds are ideal for action shots, like sports events. Slow shutter speeds are important during low-light shots, like capturing the night sky.
The shutter speed is measured in seconds, or in most cases, fractions of a second. 1/1000 is going to be incredibly faster than 1/30. In most cases, anything faster than 1/60 is going to be used, unless you’re getting a very artistic or low-light shot.
To use shutter speed with aperture, just understand that one will always effect the other. If you decide you need a really fast shutter speed, you’re preventing light from entering, so you might need to adjust your aperture setting to open the lens so your photo doesn’t end up underexposed. As another example, if you are trying to get a small depth of field, you’re aperture is going to be set at a fairly high setting (f/2.8). This is going to allow a lot more light in. If too much light is coming in, the photo will be overexposed. You will need to decrease the shutter speed to fix that overexposure.
Finally, let’s go over ISO.
ISO measures the sensitivity of your image sensor. In short terms, it’s referring to how light or dark your image will. However, it’s really more than that. ISO refers to traditional photography where your film was exposed to light, and depending on how exposed it was, it effected the grain that showed up in your shots.
Imagine a grainy (or noisy) night photo. If it’s so grainy to the point that it’s hard to see the content of the photo, that means the ISO was probably set too high. If the image has no grain or noise in the background, but is also too dark to see the object of the image, the ISO was set too low.
The scale for ISO is measured in whole numbers. The most common ones you will see are 100, 200, 400, 800, 1600 and 3200. As the number increases, so does your exposure to the image sensor. A safe number to stick with is 100 because it will keep your images clean and noise-free. However, this isn’t going to work out as well when you are shooting in low-light situations.
When adjusting your ISO with your aperture and shutter speed there are some main questions you need to be asking yourself to make the adjustments appropriately.
Are you indoors or outdoors? How light/dark are your surroundings?
If you are in a well-lit room, chances are you won’t need to set any of your settings super high or low because the light should be just fine for capturing what you want to capture.
If you are outside and it’s bright out, you will want your ISO set to 100, and your shutter speed to a faster pace. Now you can focus on setting your aperture to allow the perfect amount of light in.
If it’s cloudy outside, you can bump up your shutter speed and adjust your aperture to allow in more light. Unless it’s really dark, you should usually keep your ISO below 400.
Are you capturing objects in motion or a stationary object?
You want the fastest shutter speed possible to capture the least amount of blur. You will also want everything in focus, so the aperture should be set at a smaller hole (so a higher number, technically). If you aren’t getting in enough light because of these settings, you will probably need to bump up your ISO to a higher number, depending on how light your surroundings are.
If you want a blurry action shot (lights in motion), you will want a slower shutter speed.
Are you focusing on one object/person in particular or do you want the entire shot to be in focus?
Adjust the aperture to get the depth of field that you want, and then adjust the shutter speed then the ISO to correct any exposure problems with your shot. If you are trying to get a wider aperture for a portrait shot, you will probably need to adjust your shutter speed to bring in a little less light.
If you want the foreground and background in focus, you may need to increase your shutter speed by a small amount to bring in more exposure to the overall image. Depending on how light or dark your surroundings are, you will need to adjust the ISO accordingly.
Do I have a tripod?
If you don’t have access to a tripod, you will be limited to the type of shots you can take. If you are shooting with a shutter speed slower than 1/60, you will need a tripod to avoid a blurry shot.
Tripods are also useful in taking multiple photos one after the other, so your position doesn’t move between shots.
Although it seems like a lot to take in, once you understand the trifecta of photography, you will feel a lot more confident with your camera and setting up your shots. Just remember, there is no technical ‘good exposure’ level. You are the artist—if your aim is to get an overexposed shot, or a blurry motion shot, then adjust your settings to capture that. Good exposure simply means capturing the image the way you want it.
Enjoy the process of getting the perfect photo. Don’t get frustrated when you don’t get it right away. Every ‘bad’ picture is just a learning experience for you. Once you understand where you went wrong, you can adjust your settings until you get the photo that you were striving for. Experiment with your settings, too. Who knows, maybe you’ll discover you love the way an image turns out when you were initially aiming for something different!
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