More expensive zoom lenses have fixed aperture throughout the whole zoom range. When you zoom in to 300mm the widest aperture you can use is only f5.6 making the lens less light sensitive. The widest aperture f3.5 is only available when you zoom the lens all the way out to 28mm. Such a lens has a variable aperture depending on the focal length the lens is set to. If you have a zoom lens you’ve probably seen the aperture is given as a range.įor example, a 28-300mm lens can have an aperture of f3.5-f5.6. How much light a lens collects at a given aperture depends on the focal length. The confusing part is sometimes we refer to a smaller opening in the lens while we other times refer to a smaller f-number. Different terms used for aperture can be confusing You simply need to think opposite to understand what aperture is. With a bigger f-number you let less light into your camera. The counterintuitive effect of using ratio to measure aperture is, the smaller f-number, the more light is let into the camera. As an example, a zoom lens at 200mm and f2,8 let the same amount of light into the camera as a fixed focal length lens at 50mm set to f2.8. Provided shutter speed and ISO are unchanged, you maintain the same exposure for a given aperture (f-stop) independent on which lens you use or its focal length. Using ratio is a way to standardize and make aperture independent of which lens and focal length you are using. The f-number is the ratio between the focal length and the effective size of the aperture opening of the lens. How is aperture measuredĪperture values are given as f-numbers. A wide opening let in more light and a small let in less light, which is logical. The purpose of the aperture is to control how much light you let into the camera sensor. The mechanical part is a diaphragm made of several blades which can be adjusted to change the size of the opening. Simply explained aperture is the opening inside the camera lens. What is aperture is a common question when you start with photography.
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