It’s All About Light

Most of photography is all about controlling and/or manipulating light. There are three factors that come into play in this effort. One is the camera’s f-stop. This is the diameter of the aperture in the lens, which is much like the iris of your eye. What confuses most people is that the larger the f-stop number, the smaller the lens opening. It might be easier to remember that the bigger the number, the more light is stopped. Maybe not.  Anyway, if your camera is set to f4 for example, the lens aperture is wide open: stopping the least amount of light. If you set it to f16, then the aperture is substantially smaller, stopping much more light. Imagine your iris in a dark room. It is opened as wide as necessary to allow as much light in as possible. As soon as someone turns on the lights, your iris closes down to reduce the light entering your eye. The camera’s aperture works the same way.

The second factor is the shutter speed: how fast the shutter opens and closes. This is usually measured in fractions of a second, for example, 1/250 or 1/500. The faster the shutter speed, the higher the bottom number. And the higher that bottom number, the less light is allowed in. So, shooting picture at f4 and 1/100 second is going to let a lot of light into the camera.

The third factor is the speed of the film. Most general purpose film has a speed (referred to as an ASA or ISO number) of 100 or 200. This is also considered “slow” film. Fast film which requires less light to make an impression would be numbered as 800, 1000 or 1600. The down side to faster film is less quality, or an increase in the “graininess” of the negative.

So what does this all mean for digital photographers? Most digital cameras and many film cameras have a fully automatic setting. In this mode the camera determines the optimum settings for the f-stop, the shutter speed and the “film” speed. Cameras also have the capability to allow for changing these settings to f-stop controlled or shutter speed controlled. In these modes, you can select either the f-stop setting you want or the shutter speed you want, and the camera will automatically adjust the remaining settings to compensate.

Most digital cameras also have icon settings for portraits, landscape, extreme close ups, and sports. In these settings the camera again makes the determination on the optimum settings, but most of these are governed by the f-stop. For example, in the setting for extreme close ups, or macro photography, the camera will usually opt for a low f-stop: f4 or f5.6. This allows the camera to select a faster shutter speed which will help reduce vibrations or movement that would otherwise blur the picture. In the sports setting, the camera will normally opt for a fast shutter speed and a fast “film” speed to allow quick action to be stopped, again reducing blur. So, if you want to include blurred lines in a sports picture to dramatize the motion being captured, you should not choose the sports setting.

Given this, what settings do you think the camera would choose for portraits and landscapes? I’ll cover this when I talk about depth of field.

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