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If you have been doing photography for any amount of time, you probably have heard the term f-stop. Aperture is another term for f-stop and they get used interchangeably. But what does f-stop mean and why is it important to photography? In this article I am going to explain what f-top is and how you can use it to enhance your photography.
A camera obscura in its most basic form is a darkened room with a pin hole somewhere in the room. Since everything else in the room is blacked out, light can only enter through the pinhole. Whatever light flows through the hole becomes an upside down image that gets projected across the room. Painters and creatives would use camera obscura’s before cameras were invented to survey the land. You can easily make a camera obsucra at home by blacking out all of the windows of a room with thick black plastic. Poke a small hole in one of the sheets of plastic and wait for your eyes to adjust. You will see whatever is outside appear on the opposite wall and it will look like a projector image. Its really cool!
This is a depiction of a camera obscura, the man image is displayed upside down inside the room.
In a camera obscura the hole that the light flows through is the f-stop. F-stop is the hole that lets light into a camera. In older cameras there was not as much control over the f-stop, but with modern digital cameras you have full control. You can make the size of the hole either really small like a pinhole camera or really large to let lots of light in. There are many different reasons why you would want to control your f-stop. When we make the hole in the lens bigger its called opening up the lens and when we make it smaller its called closing down the lens.
Related article: The Basics of Aperture Size
There are three ways of controlling the light that comes into your camera. These are ISO, F-stop or aperture, and shutter speed. ISO is the light sensitivity of your digital sensor. The higher you push your ISO the more fuzzy your images will look. But cameras are getting better and better at processing high ISO images. Aperture or f-stop is the size of the hole in your lens. The bigger the hole the more light gets let in, the smaller the less light. Lastly shutter speed is the amount of time that your shutter is open letting light flow into the camera. If you are shooting handheld the rule is that your shutter speed cant be any slower than the length of your lens. For example if you are shooting on a 200mm lens you cant shoot any slower than 1/200th of second.
This chart shows the relationship between ISO, f-stop, and shutter speed.
Depth of Field
You will often hear the phrases shallow depth of field and deep depth of field. Shallow depth of field is when a photograph is taken with a very large f-stop. The reason this is called shallow because the actual focal plane is very short. Deep depth of field means that the focal plane is very wide. Generally you would use a shallow depth of field for portraits and a deep depth of field for landscape photography.
Its easier to understand depth of field if you can look at it from this angle.
Since a larger f-stop means that more light is being let in, its great for low light situations. This is why pros love using prime lenses with huge apertures so they can shoot in dark situations. A large f-stop is great for getting those beautiful images with blurry backgrounds. It gives images that “professional” look that everybody wants. Using a large aperture is also great for pointing to specific things in an image. A great example of this would be a classic ring shot in a wedding. Photographers use super large f-stops to put all the attention on the diamond.
One thing you have to be aware of when using a large f-st0p is the very shallow depth of field. When you are photographing a single person this usually comes with no issues. As long as you get good focus on their eyes, you can create a beautiful portrait. When you start photographing more than one person things can get a little more complicated. If you are shooting more than one person and you want to use a large aperture just keep them in the same plane. Every f-stop has a different focal plane. For a very small f-stop such as f/22 it may be 20 feet. But when you get down to f/1.2 that measurement changes to a few inches. Just try to keep your subjects faces in a similar line. Thats why photographers usually want groups of people to line up shoulder to shoulder for a photograph.
This is a depiction of shallow or narrow depth of field.
A smaller f-stop is also a great asset to photography and one you can use often. Using a very small aperture will give your images an overall sharpness. Its great to use a small aperture while doing landscape photography so everything in the image is sharp. A lot of studio photographers keep their camera at around f/8. This is a nice kind of middle ground aperture. It keeps things pretty sharp while allowing the shutter to not go too low. Shooting with a small f-stop can come with its difficulties though. If you are ever in a low light situation its just not feasible to shoot at f/16 while holding the camera by hand.
You would also think that it would be great to shoot with a very small aperture for star photography. This is also very difficult because the earth is rotating. Any exposure of the stars longer than 30 seconds will result in blurry start because of rotation. So if you are closing down your lens, make sure its a bright sunny day or you have very bright strobes.
Related Article: Night Photography: 5 Tips For Beginners
Since everything is in focus, this image was shot with a very small aperture.
F-stop, aperture, closing down, opening up, camera obscura, these can all be very confusing. I hope you were able to get a clear understanding of all of this camera jargon. F-stop is a crucial part of photography. It allows us to obtain beautiful blurry backgrounds and nice sharpness throughout an image. Just keep in mind all the creative control you have with photography and remember to use your f-stop wisely.