This week we are striping it right down to the basics of photography. Photography is all about light. LIGHT. LIGHT. LIGHT. Cameras record light in all its myriad of shades and colours which then form the photographs you take. There are three mechanical functions in a camera that deal with light: aperture, shutter speed and ISO. Aperture lets the light in, shutter speed dictates how much light is let in and ISO determines how sensitive the camera’s sensor is toward light. These three functions impact exposure. Aperture, ISO, shutter speed and exposure are the four pillars of photography, and the four most important elements to get to grips with. Exposure, ISO, aperture and shutter speed are to photography what addition, subtraction, multiplication and devision are to mathematics. These photographic functions are the building blocks without which we could not possibly understand how photography works and how to take the photographs you want. In order to take the step from happy-go-lucky point-and-shooter to a budding photography professional, you absolutely need to understand what these pillars are and what impact they have on your photograph. If you get the grips with the basics, you can then begin to develop your creative tools of personal style and produce kick-ass images in no time at all.
Exposure is the amount of light captured by your camera when a photograph is taken. If there is too much light captured, the photo will be washed out or overexposed. If there is not enough light captured by the camera then you are left with a photograph that is too dark or underexposed. Aperture, shutter speed and ISO all directly effect exposure. You cannot change exposure, rather you must change aperture, ISO and shutter speed to get the exposure you want. You need to get the balance between the three functions right in order to correctly expose your image. Exposure really is the result of the the corresponding relationship between aperture, ISO and shutter speed.
Aperture can be confusing to grapple with initially. I found it helpful in the beginning to think of aperture working like a human eye. The front element of the lens works to direct and control the direction of all external light just like the cornea would in directing light to the iris of an eye. Aperture works in a similar way to that of an iris by either expanding or contracting to allow more or less light in. In doing so, the depth of field in the image is impacted. Depth of field refers to the sharpness or focus between the nearest and farthest object in an image. A shallow depth of field will have only the fore subject in focus whereas a deep depth of field will clearly show detail of the background to the subject. Aperture is expressed in f-numbers (for example f/5.6). These f-numbers (known as “f-stops”) are a way of describing the size of the aperture, or how open or closed the aperture is. A smaller f-stop number means a larger aperture and a shallower depth of field, while a larger f-stop number means a smaller aperture and a deeper depth of field.
Shutter Speed is just that – a measurement of the time it takes for the shutter to open and close. Referring back to our analogy of the eye, shutter speed can be thought of as similar to the action of a blink. When we blink our eye lids close for that split-second, momentarily closing off the visual information or light we were looking at. The picture we form of what is before us is briefed by the light or information we are exposed to while our eye lids are open. In a camera, this information would then be relayed onto the cameras sensor and for us it is relayed onto the brain. Shutter speed thus controls the length of time light is allowed to enter the camera and consequently how much light is recorded on the photosensitise surface, which in a DSLR is the camera’s digital sensor.
Shutter speeds are listed as whole seconds or as fractions of a second. The maximum shutter speed for most DSLR cameras is 30 seconds. Setting a slow shutter speed will allow you to capture a sense of movement in a photograph, allowing the movements of cars, people or animals for example to be recored on the digital sensor for as long as the shutter is open, thus giving a visual representation of movement in the image. This is known as motion blur. A low shutter speed will also show camera shake (think of a slight tremble of the photographers hand or movement while the shutter is open) in an image – the slower the shutter speed the more able the camera will be at capturing movement or motion blur. A fast shutter speed on the other hand, freezes motion in time. The faster your shutter speed, the more direct and distinct a moment in time is recored.
ISO or International Standards Organisation is the standardised industry scale for measuring sensitivity to light. Gahh! The dudes at the International Naming Boarding for Things could not have come up with a less sexy name if they tried. There I was thinking ISO stood for Image Sensitivity to Obviously-everything. Aperture and shutter speed will give you your desired creative effects but will impact the amount of light the sensor receives. ISO controls how much light is detected by the camera’s image sensor. As a rule, you want to keep ISO to as low a number as possible as the image sensor’s sensitivity to light is increased with ISO – meaning if ISO is too high in correlation with the aperture and shutter speed settings, your photograph will be too ‘noisy’ or put another way, will contain grain. Ensure that your settings allow the camera to adequately deal with the available light in order to produce the image you want.