An interesting discussion that comes up in digital photography(and indeed photography in general) is that of aperture vs f/stop. So what exactly is aperture, what is f/stop, and what is the difference or similarity between the two? Let’s find out.
Aperture is the actual size of the opening of the lens: how much light is being let in. F/stop is a numerical setting for aperture. Lower f/stop numbers mean larger apertures, and higher f/stop numbers mean smaller apertures.
What is aperture
Aperture is a measure of the amount of light the lens of the camera is letting in. The aperture is usually denoted on the camera in terms of an f/stop, which we will talk about later in the post.
Generally speaking, a large aperture means more light comes in to the camera. Smaller apertures result in the opening of the lens being smaller, so less light enters the camera.
A good way to think about aperture is looking at how the human eye works. Your eye has a mechanism to control how much light enters. If you are in low light conditions, the iris of you eye expands to let more light in. The more light that comes in, the better an image you can see.
The opposite is true in bright conditions. Here, there’s a lot of light on the outside, so you don’t need to let as much in to get a good image. Your iris contracts, and that limits the amount of light let in.
In most modern cameras with auto shooting modes, you don’t really need to worry about setting aperture manually for every shot. Auto modes do a pretty good job of taking decent photographs.
However, when you set the camera into manual mode, you can really tweak the photographs to get a whole range of effects.
To configure aperture, your dSLR camera will probably have an A mode and an M mode. The A mode stands for aperture priority, in which you can adjust the aperture manually and the camera will automatically adjust the other settings to match.
In M mode, which stands for manual, you can change the aperture and all of the other settings as well.
Aperture and exposure
One of the first places you’ll see an effect by changing the aperture is in the exposure of the photograph. In large apertures, since the opening of lens is now bigger, more light is let in, so the photograph will have more exposure.
In very bright conditions, using the maximum aperture can result in a photo which is way too bright and perhaps even washed out because of all the light.
In very dark conditions, using the minimum aperture can result in a photo which is too dark.
One of the best ways to learn how your camera sensor responds to changes in aperture and the effects that has on the exposure of your photographs is to simply crank it up to maximum aperture, take a photo, then go down to minimum aperture, and take another photo.
You can then compare the two images to see how the camera behaves at extremes, and start adjusting in between.
Size of the aperture and depth of field
A really cool effect you can create using aperture is adjusting the depth of field. Depth of field is a way of showing how much of the subject is in focus.
Shallow depth of field(also known as thin depth of field) is where the background is blurred out completely, and only the foreground is in focus. A large or deep depth of field is where the background and foreground are both in focus.
Large aperture settings will decrease the depth of field, resulting in what you’d call shallow or thin depth of field. This setting is actually ideal for taking portraits or any kind of photo where you only wish to focus on the subject and nothing else.
Smaller aperture settings will increase the depth of field, resulting in what you’d call a deep or large depth of field. This setting is ideal for taking landscape photos where you’d like the focus to be uniform across the entire photograph.
Another way to think of this is that aperture plays around with the focal length. You can achieve a similar result by manually focusing the lens to keep the foreground in focus and blur the background(or vice versa).
The easier way to do it is just by adjusting aperture to change the focal length, though. In photography, the effect you can achieve by adjusting the focal length through aperture settings is called bokeh.
Size of the aperture and shutter speed
Next up, let’s talk about the size of the aperture and its relationship to shutter speed.
In a larger aperture setting, where more light is entering the camera, you’ll need to increase the shutter speed because more light can enter in less time thanks to the larger opening in the lens.
In a smaller aperture setting, where less light is entering, you’ll need to decrease the shutter speed because less light can enter, and you need more time to let enough light reach the sensor.
This is important to remember! If you crank up the aperture and use a slow shutter speed, the entire photo will just be a big blob of light with no details whatsoever.
The same thing goes for the opposite – if the aperture is very small and you have a fast shutter speed, you’ll end up with a really dark photo.
In Aperture priority mode(A mode), your camera will handle shutter speed for you, so you don’t need to worry about adjusting it. That does not mean that you can set aperture to anything and end up with a good photo, though!
If you set the aperture very small and you’re in low light conditions, the camera will compensate by decreasing the speed of the shutter, so unless you’ve got the camera mounted on a tripod and/or your subject is still, your photo will end up blurry.
F/stops or f/numbers
F/stops or f/numbers are a measurement of the aperture. Things can get a little confusing here because smaller f/stop numbers indicate larger apertures, and larger f/stop numbers indicate smaller apertures.
This is counterintuitive at first, but you’ll get used to it soon enough.
While we’re at it, let’s talk about some f/stop ranges and see what kind of images they’d produce.
f/0.95 to f/1.4
f/0..95 to f/1.4 are super high apertures and only available on professional lenses. These are suited to extreme low-light photography(think night sky, dimly lit parties), and if you use such an aperture for shooting portraits or close-up shots, you’ll notice that the subject will pop out of the background due to the extreme depth of field.
f/1.8 to f/2.0
Pro-hobbyist lenses sometimes go to these levels, and while not as good as f/0.95, it will still produce respectable images in low light conditions. This level is still good for shooting really nice up-close shots.
f/2.8 to f/4
The f/2.8 to f/4 range is what you’ll find in most zoom lenses. Obviously, these won’t be able to capture as much light as the lower f/stop lenses, but they’re still pretty decent and can get you good depth of field for everyday shooting conditions. You can also use this range for sports, wildlife, or travel photography.
f/5.6 to f/5.8
f/5.6 to f/8 is great for landscape photography where the size of the lens opening is just enough to get a good depth of field to capture as many details as possible. You can also use this aperture setting for taking photos of large groups of people where all the subjects need to be as sharp as possible.
f/11 to f/16
In situations requiring extreme depth of field, like large, sweeping landscapes or buildings, these are the ranges you need your f stops to be in. Below f/8, you’ll start losing sharpness, so be careful.
Minimum and maximum aperture of lenses
An important thing to remember is that not all lenses are equal when it comes to aperture. Lenses have a physical limit on the opening of the aperture: how large or small it can be.
Maximum aperture is very important, and probably more so than minimum aperture, because that will determine how much light can enter the sensor in total. This is a good way to measure how your camera performs in low light conditions.
As far as large aperture is concerned, a lens with a rating of f/1.4 or f/1.8 can open up pretty wide and let in a lot of light. These are also termed fast lenses.
Other budget lenses sometimes have the biggest aperture rated at f/4.0. For larger apertures, you’ll need to be prepared to shell out more cash.
The upper limit is more important than the lower limit because most lenses can go down to f/14 or f/16, which is really more than enough for most use cases.
Aperture and zoom
Here’s where things get interesting: when you zoom in and out, the limit for aperture changes on many lenses. This does not apply to all lenses, but most, especially the ones that cameras often ship with.
You may see that when you are zoomed out all the way(wide), the aperture will be on the lower end at f/3.5, but if you zoom in all the way, the aperture will shrink to f/5.6 or so.
There are lenses available that can maintain the aperture while zoomed in and zoomed out all the way, but again, you’d have to be prepared to shell out more cash.