The center has the ball and is the mid point in the string of offensive linemen. You are on the sidelines and the team with the ball sets up on the line of scrimmage directly in front of you. So let's say you are photographing a football game. Let me show you this concept in a sports photography context. If you took a photo of your hand, you have the ability to put your hand in focus and let the background go soft (blurry) or keep them both in sharp focus depending on how you set your aperture. Every time you shoot a photo, you have the ability to control which subjects are in focus and which things are out of focus. Notice how your hand is now out of focus? The term depth of field is simply the art of controlling how much of your photo is in focus. Do you notice that once you focus on your hand that everything in the background goes out of focus? Now leave your hand there, leave one eye closed, and focus on the background. Hold your hand up in front of your face, close one eye and now focus on the details of your hand. Is your range of focus shallow or deep? Here is a simple exercise to help explain this concept. Sometimes f/1.3 and f/3.2 and other differences are used for the one-third stop scale.So why the heck do photography terms sound so complicated? Considering photography is basically an art form, why is the language so darn scientific? Depth of Field? What does that mean and why is it relevant within the world of sports photography? Well I am here to demystify all the pomp and clutter and cut through all the confusing terminology.ĭepth of Field is just a fancy way of describing what is in focus in your photo. Sometimes the same number is included on several scales for example, an aperture of f/1.2 may be used in either a half-stop N = f D Ĭonventional and calculated f-numbers, full-stop series: The numerical aperture takes into account the index of refraction of the medium in which the system is working, while the f-number does not. The f-number is related to the numerical aperture of the system, which measures the range of angles over which light can enter or exit the system. A lower f-number means a larger relative aperture and more light entering the system, while a higher f-number means a smaller relative aperture and less light entering the system. The relative aperture indicates how much light can pass through the lens at a given focal length. The f-number can also be interpreted as the inverse of the relative aperture (the aperture diameter divided by focal length). The f-number is a dimensionless number that is usually expressed using a lower-case hooked f with the format f/‘‘N’’, where ‘‘N’’ is the f-number. The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is a key factor in determining the depth of field, diffraction, and exposure of a photograph. It is calculated by dividing the system's focal length by the diameter of the entrance pupil (“clear aperture”). Diagram of decreasing apertures, that is, increasing f-numbers, in one-stop increments each aperture has half the light-gathering area of the previous one.Īn f-number is a measure of the light-gathering ability of an optical system such as a camera lens.
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