What Is F Stop In Photography

By | 08/09/2022

The camera on an iPhone.
Apple

As smartphone cameras become more than capable, technical photography jargon is slipping into mainstream conversations. An “f-stop” (or “f-number”) is a word you’re going to see more as smartphone manufacturers effort to one-upward each other when bragging about specs. Here’due south what y’all need to know.

Aperture and the Exposure Triangle

Aperture is one of the iii legs of the exposure triangle, along with shutter speed and ISO. Information technology’southward a measurement of how wide the hole is at the forepart of a lens and, thereby, how much light it allows in. Shutter speed measures how long calorie-free is allowed to hit the sensor and ISO measures how sensitive the sensor is.

While shutter speed is measured somewhat intuitively in fractions of a 2d, aperture is measured in f-stops, such as f/i.6, f/11, and f/22. Most lenses allow you to adjust the f-end, although smartphone cameras are an exception; they take a fixed aperture. Lowering the f-finish makes images brighter, while increasing it makes them darker.

Simply how does it do this?

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What Is Aperture?

F-Stops Simplified

A diagram of lens aperture values from f/1-f/32.
Oleksii Arseniuk/Shutterstock

The f-stop is the ratio of the focal length of a lens to the lens aperture (the hole through which the light enters). So, an f-finish of 2 (f/2) means the lens discontinuity is half the focal length. In a lens with a focal length of 100mm, the aperture would be 50mm (100/50 = ii); in a lens with a focal length of 200mm, the aperture would be 100mm (200/100 = two).

An f-terminate is measured as a ratio due to some of the fun quirks in the physics of optics.

The wider the aperture of a lens is, the more low-cal information technology allows through. This makes the image information technology projects on the moving picture plane—or, realistically, the digital sensor—brighter. So, the lower the f-number, the brighter the prototype.

However, lenses with longer focal lengths have narrower fields of view. That’s why the images they projection are relatively larger and spread the low-cal thinner. The mode the furnishings remainder out ways the ratio of focal length to the aperture (or f-number) creates photos that are equivalently bright with all lenses. It ignores any differences in light transmission.

Two images of a man fishing at sunset shot at different focal lengths, but with the same amount of light.
Both of these photos were shot at f/8, only at different focal lengths. They used the same shutter speed because the bigger aperture of the longer lens was offset by its narrower field of view.
Harry Guinness

For example, say y’all’re taking a photograph of a tree. If y’all utilise a 100mm lens at f/2, the aperture volition be 50mm wide. If yous use a 200mm lens at f/two, the aperture will be 100mm wide. Both photos, however, volition exist merely equally brilliant.

This is considering even though the 200mm lens has an aperture that’due south twice as wide (and thus, four times every bit large), its field of view is half that of the 100mm lens. Therefore, it has to project everything iv times larger on the sensor, then the two furnishings cancel each other out.

F-Stops in Photography

At present that we’ve covered the technical details, permit’south expect at how f-stops employ in practical photography.

Taking a photo involves balancing the aperture, shutter speed, and ISO. Y’all desire enough lite to hitting the sensor so information technology records the scene properly, but not and then much that it’s too dark (underexposed) or bright (overexposed).

The corporeality of light that hits the sensor is measured in a dimensionless quantity chosen a “stop.” Increasing the exposure (the brightness of the photo) past one cease ways you double the corporeality of light hitting the sensor. (Other things that touch on exposure, similar image stabilization, are also measured in stops.)

There are a few means you can do this. One method is to allow calorie-free to hit the sensor for a longer amount of time, such equally using a shutter speed of i/50 of a second instead of 1/100. You could also but use a wider aperture, but this comes with some trade-offs.

A portrait of a woman on the left and a man skiing down a mountain on the right.
In DSLRs and other defended cameras, aperture controls the depth of field.
Harry Guinness

In addition to allowing in more light, images shot with a wider discontinuity have less depth of field, meaning more of the scene will be out of focus. Sometimes, such as when shooting a portrait, this is desirable. Other times, information technology’s a problem you have to work around.

To make matters even more confusing, discontinuity isn’t measured on a linear scale. F-stops are logarithmic. In other words, going from f/4 to f/2 doesn’t double the amount of lite entering the photographic camera, information technology quadruples it. To double the corporeality of light, y’all’d need to go to f/2.viii.

Yeah, that’s a lot of information to process. Fortunately, though, considering smartphones take fixed aperture lenses, yous don’t have to fully understand this to employ them finer (more on this beneath).

Yet, if you also use a dedicated camera, yous might want to learn more near how y’all can utilise discontinuity creatively in photography.

F-stops and Your Phone

The specs of the telephoto lens on an iPhone 11 Pro.
That doesn’t look like a 26mm aperture hole to me.
Apple

Both amateur and professional photographers accept had to come to terms with f-stops and aperture over the years. Now that smartphone manufacturers are using these terms in their marketing, hither are a few things everyone should go along in mind:

  • F-stops are calculated from a lens’s real focal length: While the f-numbers manufacturers list are existent, the focal lengths they boast for their lenses are usually a full-frame equivalent. For example, Apple tree claimed the telephoto lens in the iPhone xi Pro was 52mm with an aperture of f/2. This would mean light would laissez passer through a pigsty over 1 in. wide. However, the real focal length was simply 6mm, so the hole was merely 3mm wide.
  • A wider aperture means ameliorate low-lite photography: Due to how smartphone cameras are designed, the fixed aperture’s biggest event is on the shutter speed and ISO the photographic camera can use in different situations. The wider the fixed discontinuity of the lens, the better the images in low low-cal. This is because information technology tin use faster shutter speeds (for less blur) and lower ISO (for less racket).
  • Specs don’t have photos: As companies continue to throw around crazy numbers, just remember those aren’t what creates a skillful photo. The iPhone Photography Awards started 13 years ago because people have been shooting awesome photos with smartphones for equally long every bit they’ve been around. The fact that the camera on your phone can go from f/1.8 to f/ane.vi isn’t going to drastically better your photography—only time and effort can exercise that.

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Source: https://www.howtogeek.com/695949/what-is-f-stop-in-photography/