The aperture opening is measured in f-stops, which are, in fact, a fraction. For one thing, f/2.8 is a pretty weird number, but how can f/2.8 be a larger aperture opening than f/4? Look how dusty it is, though! Ugh.Īperture is the one that always trips up my students, because it appears as if the F-stop scale doesn’t make any sense. F-stops and apertureĪ lens, fully stopped down. The scale of F-stops is a geometric sequence of numbers: the sequence of the powers of the square root of 2. At ISO 400, it multiplies everything by 4 - and so on. At ISO 200, it’ll take your light measurements and multiply them by 2 (because it used half the shutter speed in its exposure calculation). When you’re shooting at ISO 100, your camera will use the light capture data as-is. These days, it refers to the sensitivity of your light sensor (or rather, a multiplication factor done by your camera’s processing chips). ISO deals with light sensitivity in the old days, we’d talk about film speeds of a certain ISO. The same goes for 1/100 and 1/200 - the former is half as fast as the latter. As I hinted at before, they are both pretty intuitive: A 2 second shutter speed means that the shutter is open twice as long as a 1 second shutter speed. ISO and Shutter speedsīefore we dive into aperture-land, let’s take a look at shutter speeds. In other words: if you shoot a photo at 1/100 second, f/4 and ISO 200, you would get exactly the same brightness in your photo if you halved the ISO and doubled the shutter speed (so 1/50 second and ISO 100) or the other way around (1/200 second shutter speed and ISO 400). That is you can use two different sets of exposure settings, that let the same amount of light onto your light sensor. It may also be necessary to use a higher ISO setting when shooting with a narrow aperture or high shutter speed - since a narrow aperture and high shutter speed reduce the amount of light that strikes the image sensor.It’s sort of important to know what ‘half the aperture’ is of any given aperture, because if you’re shooting in Manual mode (you’re not still shooting in automatic modes, are you?!), you can use something called ‘synonymous exposures’. When shooting in low-light situations, a higher ISO (400 or above) is recommended. Therefore, in well-lit environments, a lower ISO (200 or below) should be used. A lower ISO number decreases the sensitivity and requires more light to produce a correct exposure. A higher ISO number increases the sensitivity this means that less light is needed to produce a correct exposure. ISO determines the sensitivity of the camera sensor to light. Essentially, using a fast shutter speed with a wide aperture can provide the same amount of light to the image sensor as when using a slow shutter speed with a narrow aperture. For example, 1/30 at F5.6 is the same as 1/8 at F11. You can get the same amount of light if you change the shutter speed and aperture settings at equivalent amounts. NOTE: There is a reciprocal relationship between shutter speed and aperture. IMPORTANT: Changing the shutter speed also affects motion blur. Shutter speeds can vary from fractions of a second to several seconds in duration. If the camera shutter is left open for a shorter duration, less light is allowed inside the camera this is achieved by using faster shutter speeds (such as 1/250 or even faster). The longer the camera shutter is left open, the more light that is allowed to enter the camera this is achieved by using slower shutter speeds (such as 1/60). Shutter speed also can affect the amount of light that comes into the camera by controlling how long the camera shutter remains open. IMPORTANT: Changing the aperture also affects the depth of field. On the other hand, Higher f-stop settings (such as F11) have a smaller diaphragm opening, allowing less light through the lens. Lower f-stop settings (such as F5.6) have a larger diaphragm opening, allowing more light through the lens. The aperture settings are commonly referred to as f-stops and have a specific numerical sequence, such as F5.6, F7.1, F8, F11 and so forth. It affects the amount of light that passes through the lens and is usually made up of a set of blades that open or close depending on the aperture setting selected. The lens aperture is a diaphragm that is in the lens itself or immediately behind it. The ISO affects how much light is needed to produce a correct exposure. Two controls affect the amount of light that comes into the camera and strikes the image sensor - aperture and shutter speed.
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