What Is F-Stop?

So, you've probably heard the term "F-stop" thrown around a few times if you're into photography. If you're not, don't worry—we'll explain it! A F-stop is a ratio that describes the size of an aperture (the iris in your camera lens) relative to its focal length. The "F" stands for "focal," which means measuring the distance between the lens and the subject. The number itself is called an f-number or f-stop. When you set your camera to a low F-stop, you may need to increase your shutter speed to let in enough light. You can also set your camera to a high F-stop and slow down your shutter speed to create a shallow focus effect. As with ISO, it's essential to know how each F-stop setting on your camera affects shutter speed to adjust accordingly. The f-stop is a measurement of the size of the aperture in your camera lens. It's like your camera's version of an eye pupil—it lets light in and out. The f-stop scale is marked by a hooked f (f), as in "f/5. " The smaller the number, the larger your aperture, and vice versa. A low f-stop number would be ideal for dimly lit areas, allowing lighter to enter through the lens. The opposite is true: A higher f-stop number would be suitable for brightly lit areas because it will restrict how much light can enter the lens. F-stop is sensitive to light fall-off, meaning that if you're taking a picture close (like with a macro lens), there will be significant light fall-off at the edges due to the wide angle of view. This can often lead to images of brighter things at the center than at the border. Get ready for this: if you increase your shutter speed (by lowering the ISO), your desired exposure time will be shorter at any given aperture, meaning that the crack needs to be wider (lower f-number) to maintain proper exposure!