Photography 101: How to Use a Camera
Photography is a fun and enjoyable hobby for many folks. And today’s cameras make photography easier than ever, their automatic functions make creating great photographs as simple as pressing a button.
But what exactly is a camera doing? How do the various controls work together to make a photograph? And what effect do those controls have on the finished image?
A camera is simply a light-tight box that controls how light hits a recording medium. That recording medium used to be film, but now it is most commonly a digital sensor. While the technology differs, the operation of the camera is essentially the same.
Every camera ever made has three functions that control how the sensor is exposed to light. They are aperture, shutter speed and ISO. Many cameras have a great many more functions than that, but these three are all that is required to make a photograph.
The first function is aperture. Aperture is the hole in the lens through which light passes on its way to the sensor. All cameras have apertures, better cameras will allow you to choose the size of the aperture when making a photo. Aperture size is designated by numbers known as f-stops. Common f-numbers for aperture are f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Smaller f-numbers, like f/2, mean a larger aperture. And larger f-numbers, like f/22, indicate a smaller aperture.
In addition to controlling how much light passes through a lens, aperture also controls how much depth of field the finished photograph will have. Depth of field is the distance in front of and behind the subject that also appears to be in focus.
A photograph in which only the subject is in focus and where objects in front of and behind the subject are rendered as fuzzy shapes is said to have shallow depth of field. To make a photograph with shallow depth of field, a photographer must use a larger aperture such as f/2. Portraits commonly use shallow depth of field to emphasize the subject of the image.
A photograph where the entire image appears to be in focus is said to have lots of depth of field. In order to create a photograph with a large amount of depth of field, a photographer must choose a smaller aperture such as f/16 or f/22. Landscape photographers will often work to gain as much depth of field as possible to capture elements in the foreground and background of their compositions.
The next function that a camera has to control how light reaches the sensor is the shutter. A shutter is a small, usually metal curtain that sits directly over the sensor. When a photographer presses the shutter release button the shutter opens for a set amount of time, usually measured in fractions of a second. As with aperture, better cameras will allow the photographer to choose how long the shutter stays open. Common shutter speeds are 1/60th of a second, 1/125th, 1/250th, 1/500th, 1/1000th and so on. These are also referred to as f-stops.
The shutter speed setting will also determine how objects in motion during exposure will be rendered in the final photograph. Leaving the shutter open for a longer amount of time will increase the chance that objects moving during exposure will be recorded as a blur. 1/60th of a second is generally enough to freeze small movements. But subjects moving faster will require faster shutter speeds to freeze their movement. Sports photographers will work to keep their shutter speeds at 1/500th or faster to capture sharp images of athletes at work.
The third function that controls how a sensor is exposed to light is the ISO setting. ISO used to be known as film speed and was controlled by which speed film you purchased and loaded into your camera, but modern digital cameras can change the sensor’s ISO rating at the push of a button. The ISO rating is an indication of how sensitive to light the film or sensor is. Common ISOs are 100, 200, 400, 800, 1600, 3200. Lower ISOs like 100 are known as “slower” in that they are less sensitive to light and require more exposure. Higher ISOs such as 800 are referred to as fast because they are more sensitive and take less exposure to create an image.
ISO is important because it affects the overall quality of the image. The higher the ISO speed, the more film grain or sensor noise an image will have. In the days of film a photographer would use 100 speed film or slower in order to have the best possible quality image. Digital point and shoot users still need to be wary of high ISO noise, but digital SLRs have made great leaps in reducing the amount of noise visible in an image.
Modern digital cameras can be set to full automatic and a person can walk around shooting pictures that will look very nice. But to really be able to create a photograph, the photographer must be able to know how to set the controls to achieve the results he or she wants.
The conundrum comes about because all three settings must be balanced with each other and with the amount of light that is available. You can not simply pick any random aperture, shutter speed and ISO and hope to have the photograph turn out properly. For example, if the camera’s meter indicates a proper exposure of 1/250th of a second at f/16 and ISO 200 and the photographer decides to increase the aperture size two stops to f/8, then the shutter speed will have to be set two stops faster to 1/1000th to compensate for the extra light.
To make this easier, many modern cameras will have semi-auto modes that will allow the photographer to choose one of the settings while the camera will to pick the other. Aperture priority mode for example, usually indicated by the letters “Av” on the camera’s mode dial, allows the photographer to set the desired aperture while the camera picks a matching shutter speed. Shutter priority, or “Tv,” is the opposite.
So in creating a photograph, the photographer has to decide three basic things: 1. Lots of depth of field, or shallow depth of field? 2. Is the subject moving? Do I want to freeze the subject or can it blur a little? 3. How much noise is acceptable? After deciding these three things a photographer can make a conscious decision as to what camera settings are most appropriate for the photograph he or she wants to make.
But many times there has to be a compromise. A small aperture (f/16) requires a longer shutter speed so objects moving fast might be blurred so the photographer will have to choose either a larger aperture or a higher ISO.
There are many other techniques involved in creating an image. But the three discussed here are the most basic and common to every camera ever created. From the pinhole camera, home-made out of a shoebox; to the latest, greatest whiz-bang digital SLR from Canon or Nikon.