Sometimes I, like many photographers, mention the camera’s settings when posting a photograph or when explaining how to set a camera for different types of photography. These settings look much like this: f/2.8, 1/125s, 400mm, ISO: 200. These are the lens’s and sensor’s specifications during the shot and are controlled by the camera automatically or by the photographer manually on the lens or in manual mode (M), program mode (P), aperture priority (A or Av), shutter priority (S or Tv), the camera’s zoom controls, and internal menus.
Let’s take these settings one at a time.
* f/2.8 (Use A/Av, P or M mode) – This is called the f-number, and refers to the aperture (shutter opening) size. There are many common aperture sizes, denoted by f/[a number] (that number being a multiple of 1.4 or 2), which are used when photographing. As you can see from the below diagram, the larger the number, the smaller the aperture. Don’t be confused by that, though. If you’ll notice, the number (pupil diameter) is being divided by f (focal length), so, mathematically, it makes sense that the larger the number, the smaller the aperture. Practically speaking, now, the lower the f-number — the more light comes in and the narrower the depth of field [DOF – area (distance from the camera) which is in focus in a single picture].
(Use S/Tv, P or M mode) – Shutter speed. The shutter speed is how long the aperture remains open for a picture. This is in a similar format to the aperture (1 divided by a number). The larger the lower number, the shorter the shutter speed. When the shutter speed is one second or longer, it is often indicated by 1″, 1s, or 1 second. Very fast shutter speeds (like 1/1000s) are used when trying to freeze action. Slow shutter speeds are often used when photographing in low light situations without a flash or when trying to show motion.
(Zoom) – X mm (millimeters) refers to the focal length. The “standard” focal length is 35mm, which is close to what the non-peripheral part of the human eye sees. When the mm number increases, then the camera is zoomed in more. The higher the mm number, the smaller the depth of field. For those who think in terms of “x times zoom”, let’s call 35mm “1 x zoom”, since 35mm is generally the standard, widest-angle most basic cameras offer, although the number could be different. When the mm is doubled, to 70mm, you are now at 2 x zoom. Similarly, a camera at 2 x zoom probably is at 70mm. 400mm would be 11.5 x zoom.
* ISO: 200
(Film speed) – The ISO setting refers to the “film speed” or sensor sensitivity. Common ISOs are 50, 64, 100, 200, 300, 400, 600, 800, 1000, 1600, and 3200. Higher ISOs mean the sensor (or film) is more sensitive to light — the ISO is directly proportional to the brightness of a photo. One downside to high ISOs, however, is that high ISOs lead to grainy photos with a lot of noise (multiple colors showing up in splotches where there should be only one color).