Table of Contents
- 1 F-stop scale explained
- 2 Depth of Field Explained
- 3 Lens Apertures
- 4 When to Use Which Aperture?
- 5 Conclusion
As one of the factors that create an exposure (link to article about exposure triangle), aperture makes a big difference in the way your photos turn out, so it’s very important to be understood and controlled properly.
Because of its significance and its power to either add a dimension to your photograph by blurring the background or bring everything in focus it makes a very interesting subject.
It is located in the lens of the camera, and the best way to understand it is to associate it with the pupil of an eye.
It opens and closes so that it can allow a certain amount of light in, and as a pupil, the wider it is the more light it lets in.
Other than controlling the amount of light that passes through the lens, aperture also controls the depth of field.
F-stop scale explained
Aperture is measured by using f- stop scale. If you look at your camera you would be able to see ‘’f/’’ with a number.
That number represents the wideness of the aperture that affects the exposure and depth of field.
The scale is as follows:
What can seem to be confusing is the fact that the lower the number is the wider the aperture is.
For example, f/22 represents a small aperture, while f/1.4 represents a large one.
Even though it doesn’t seem logical, you should remember that, in fact, with the small number as f/1,4 the lenses of iris get wide open and therefore it lets a big amount of light trough, so that’s why it is a large aperture.
You should also know that there is an actual equation that relates to the aperture. Focal length (f) is divided by the diameter of the aperture.
For example, a lens of 50mm and the iris wide open has a hole that measures 25mm in diameter. Therefore, if you divide 50mm by 25mm it equals 2 and that number translates to an f-stop of f/2.
So, when you’re changing aperture, if you are making it smaller that is referred to as stopping down while opening up means you are making it bigger.
What you should understand is that whenever the f-stop value halves, the area that lets the light trough quadruples. There is a formula for this but you can just memorize the f- stops that correspond to each doubling or halving light:
Aperture Setting Relative Light Example Shutter Speed
f/ 22 1X 16 seconds
f/ 16 2X 8 seconds
f/ 11 4X 4 seconds
f/ 8.0 8X 2 seconds
f/ 5.6 16X 1 second
f/ 4.0 32X 1/2 second
f/ 2.8 64X 1/4 second
f/ 2.0 128X 1/8 second
f/ 1.4 256X 1/15 second
These numbers are standard options in any camera, but it is possible to have finer adjustments 1/2 or 1/3 stops, such as f/ 3.2 and f/ 6.3. The range of values is variable from camera to camera or lens to lens.
Even though the narrow aperture does not make a problem, a wider range can provide much more flexibility in creative expression.
Depth of Field Explained
Now, depth of field is the simplest function of aperture. It basically represents the amount of focus on your image around your subject. The small depth of field actually makes your subject sharper while everything else is blurry, and large depth of field makes your whole image sharp.
For example, a large f number like f/ 32, which is actually a small aperture, brings foreground and background objects in focus. Now, a small f-number like f/1.4 isolates only the foreground from the background so the objects in the foreground are sharp and the background is all blurry.
Here are some examples of photos taken with the bigger aperture:
In the examples above you can see that only a few objects appear sharp, while everything else is blurred. If a larger aperture was used, like f/ 1.4, and if it was focused on just one detail, like a letter, that letter would have been sharp and everything else would have been blurred out. So in conclusion: the larger the aperture is, the smaller the area in focus is.
There is a limit in every lens on the size of the aperture. By looking at the specifications on your lens you can learn the maximum and minimum apertures of it. The maximum aperture is much more significant than the minimum and the reason for that is because it can actually show the speed of the lens.
For example, a lens with an aperture of f/ 1.2 as the maximum aperture is taken for a fast lens because it lets trough more light than a lens with a maximum aperture of f/ 4.0. So if you are shooting in low light you should definitely use lenses with larger apertures.
Because almost every modern lens can provide at least f/ 16 as the minimum aperture, the actual minimum aperture isn’t that important since f/ 16 is more than enough for everyday shots.
There are two types of lenses:
- Fixed lens which is also known as prime
- Zoom lens
Fixed lenses have only one focal length while zoom lenses are flexible for zooming a subject in and out.
Many of the consumer lenses have apertures that are variable and the reason is the fact that the optical design for zoom lenses is much more complex. So, when you zoom out fully there is one aperture number but when you zoom in it increases the f-number to a higher number.
For example, Nikon 18-200mm lens has a variable maximum aperture of f/ 3.5- f/ 5.6. When you zoom it out fully at 18mm, the lens has an aperture of f/ 3.5, but when you zoom it in fully at 200mm, the lens has an aperture of f/ 5.6.
The professional zoom lenses mostly have fixed apertures, like Nikon 70-200mm f/ 2.8 lens has the same maximum aperture of f/2.8 at all focal lengths between 70mm and 200mm.
You are probably wondering why that’s important. The reason is larger maximum aperture which allows much more light through the lens so your camera can capture images much faster in low light situations. Other than that, larger maximum aperture also means better ability to separate subjects from the background.
When to Use Which Aperture?
The big question that comes up on the topic of the use of different apertures is what are those uses? Well, the most important thing you should know is that there are no particular rules when it comes to that – you decide by yourself. Whether you’re looking for an artistic effect or realistic reproduce of a scene in your photo, it absolutely depends on your choice.
What can be helpful in making that decision is to know the traditional uses of different apertures. Here are some.
When to use f/1.4 aperture?
This aperture is a great choice if you’re shooting in low light, but you should pay attention to the shallow depth of field. It is best used for a soft focus effect on shallow objects.
When to use f/2 aperture?
This one is pretty much the same as f/ 1.4 but is great if you are looking for a cheaper, better price of the lens.
When to use f/2.8 aperture?
It is great for low light shots but it has a deeper depth of field which allows more definition in facial features. You should know that good zoom lenses have this as their widest aperture.
When to use f/4 aperture?
If you’re taking a photo of a person on a normal lighting you would want to use this aperture because there is a risk of losing focus on the face if you use a wider one.
When to use f/ 5.6 aperture?
For photos of two people this is a great one, but make sure the lighting is good. In the case of low light make sure to use a bounce flash.
When to use f/ 8 aperture?
If you’re taking photos of a bigger group of people you should use this one because it ensures that everyone stays in focus.
When to use f/ 11 aperture?
With this aperture, your lens will be the sharpest so you should use it when you’re for shooting portraits.
When to use f/ 16 aperture?
Being a very small aperture, this one would be great for taking photos in the sun.
When to use f/ 22 aperture?
Use this one for landscapes where detail in the foreground is needed.
Just to remind you these are only guidelines, not rules. You should feel free to experiment as much as you want and explore all your options.
Whether you’re looking for taking an artistic photograph or realistic one, the aperture is something you should pay attention to, so that you can have the best outcome possible.
Even though it seems a little bit confusing because of the numbers, the f- scale can be very helpful. Just remember that the smaller the number is the wider the aperture gets and vice versa. The wider the aperture is, the bigger amount of light gets into your camera; therefore the depth of field is smaller.
Just relax, take your camera, shoot some photos and enjoy.