Archive for January, 2009

Camera Settings Explained

Thursday, January 29th, 2009

What do camera settings mean?

Sometimes when explaining how to take a certain kind of picture, photographers mention the camera’s settings and what manual modes are used for the picture. These settings look much like this: f/2.8, 1/125s, 400mm, ISO: 200. (Other settings may include white balance, saturation, or image sharpness, but I’m not going to get into that.) These are the lens’s and sensor’s specifications during the shot are are controlled automatically by the camera in Point and Shoot (P&S) models, or manually by the photographer 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 digital camera menus.


So what do all these things mean? Let’s take them one at a time…

Part 1: Explanation of the modes (M, P, A/Av, and S/Tv)

Part 2: Explanation of the settings these modes control (f-number, shutter speed, viewing angle (zoom), and ISO)


Part 1: Explanation of the modes (M, A/Av, S/Tv, P)


Typical camera dial showing various camera modes.

(The terms, “shutter speed,” “f-number,” and “aperture,” are explained below in Part 2)

M (manual mode) – In manual mode, you have control over both the shutter speed and f-number without the camera doing any automatic exposure calculations. There is often an indicator or a bar showing if your chosen values of the shutter speed and f-number will produce an over-exposed shot, and under-exposed shot, or a properly exposed shot, though it does not take into account special lighting conditions which would cause you take full control.

A or Av (aperture priority) – In aperture priority mode, you tell the camera to use a specific aperture (f-number), and the camera calculates the shutter speed needed to produce a properly exposed shot. You can also tell the camera to over-expose or under-expose the shot by a certain amount, and it will take this into account when calculating the shutter speed.

S or Tv (shutter priority) – In shutter priority mode, you specify a shutter speed for the camera to use and it calculates the corresponding f-number needed to properly expose the shot. As in aperture priority mode, you can instruct the camera with regards to how the image should be exposed.

P (program mode) – In program mode, you tell the camera to make a type of balance between an f-number or shutter speed, so it will try to use a specific value for one or both of these, but it will be able to vary from these values, if need be. As with aperture and shutter priority modes, you can tell the camera to under-expose or over-expose the shot.

ISO settings are usually accessed though the camera’s menus. Zoom is usually set with wide-angle/telephoto buttons, often found at the upper-right of the back side of the camera.


Part 2: Explanation of the settings: f-number, shutter speed, viewing angle (zoom), and ISO
(For information on what the modes do and how they work, refer to Part 1)

f-number: f/2.8 (Use A/Av, P or M mode) – This is called the f-number or f-stop and refers to the aperture (shutter opening) size. There are many, though specific, common aperture sizes, often denoted by f/[a number] (that number usually being a multiple of 1.4 or 2), which are used when photographing in various situations. The f-number can be written in different ways. For example, instead of writing f/2.8, the f-number might be written as F2.8, f-2.8, or even as 2.8. As you can see from the below aperture diagram, the larger the number, the smaller the aperture. A complete f-stop increase or decrease (like from f/8 to f/5.6 or from f/2.8 to f/4 respectively) doubles or halves the aperture size and amount of light entering the camera.

Diagram illustrating common f-stop aperture values.

Don’t be confused by the numbers, though. You might think to say that a larger number should mean a larger opening. However, it actually refers to the fraction of light being stopped by the aperture. Another (technically incorrect but more intuitive) way to think of it is to see that f is being divided by that number, so, mathematically, it makes sense that the larger the number, the smaller the fraction and total aperture size. Practically speaking, now, the lower the f-number, the more light comes in through the lens and the narrower the depth of field (DOF — distance from the camera in which objects are in focus).

shutter speed: 1/125s (Use S/Tv, P or M mode) – Shutter speed. The shutter speed is the length of time the aperture remains open for a given exposure. The shutter speed is given in a similar format to the aperture: 1 divided by a number. For example, 1/500 means that the shutter will be open for one five-hundredths of a second. As is the case with the aperture, shutter speeds can be denoted in various ways, including 1/125s, 1/125 or just by 125. The larger the number, the shorter the shutter speed. When the shutter speed is one second or longer, it is often indicated by 1″ or 1s. Fast shutter speeds (like 1/1000s) are used when trying to freeze action but decrease the amount of light entering the camera which must be compensated by widening the aperture, increasing the ISO (explained below), or by using photo-editing programs. Slow shutter speeds, like 2s, are often used for night shots or when trying to show motion. If it is bright where the picture will be taken, but one wants to show motion, one may shrink the aperture, use a low ISO, or use polarizer or neutral-density (ND) filters to block out the light.

zoom (viewing angle): 400mm (Wide-angle/Telephoto Zoom controls) – x mm (millimeters) refers to the focal length of the lens and is the camera’s zoom. The “standard” focal length is 35mm and has a viewing angle which is close to that of the non-peripheral part of the human eye sees. When the mm number increases or decreases, the camera is zoomed in more or less, respectively. For those who think in basic terms of “x times zoom,” let us call 35mm “1 x zoom” (although actual times zoom will vary by camera and lens), since 35mm is generally the standard, widest-angle on most attached-lenses cameras. When the mm is doubled, to 70mm, you are now at 2x zoom. Similarly, a camera at 2x zoom probably is at around 70mm. 400mm would be 11.5x zoom. (It should be noted that most point-and-shoot cameras actually have smaller focal lengths for the same viewing angles that an SLR camera has. So instead of 35mm it could be 12mm, but these cameras can still be said to have a 35mm “equivalent” at these focal lengths.) Greater “zooms” (higher mm numbers – telephoto shots) lead to narrower DOFs. Photos of flowers, insects and other macros are often shot at high zoom with a close focus to make the object large in the photograph and stand out against the background or foreground. Wider-angle mm numbers, like 18mm (or 0.5x zoom), lead to very wide DOFs and are often used in landscapes to take in the whole scene.

ISO: 200 (Internal camera menus) – The ISO setting refers to the “film speed” or sensor sensitivity to light. Common ISOs are 50, 64, 100200, 300, 400, 600, 800, 1000, 1600 and 3200. The ISO is directly proportional to the amount of light it senses. In basic terms, higher ISOs mean the sensor (or film) is more sensitive to light, while lower ISOs mean the sensor will be less sensitive to light. The main downside to higher ISOs is that high ISOs lead to noisy and grainy photos with less details. (Photo noise is two or more colors which are similar in brightness or color to one another showing up where only one solid color should exist.) Low ISOs are usually used in long-time-exposures (LTEs) because they are less-sensitive to light and better preserve detail than high ISOs.