Exposition in photography: what is it

The term "Exposure" means the amount of light that enters the photosensitive photographic material for a certain period of time. The three main parameters that affect exposure are sensitivity, shutter speed, and aperture. Most modern cameras, whether analog or digital, automatically control these three parameters. Some compact cameras have manual control functions, and all SLR cameras provide the photographer with full manual control over all parameters, functions and settings. How does the camera determine shutter speed, aperture, and sensitivity? If the answer to this question is not so obvious for you, then do not worry, we can figure it out together. Many aspiring photographers find the issue of exposure too difficult to understand. But one has only to deal with the terms, and everything becomes clear and simple. Understanding the essence of determining the correct exposure lenses, you can explain to yourself the reasons for the appearance of blurry, dark or too light images, which are so frustrating for beginners. You will also understand what your camera is capable of in various situations.

Diaphragm

Aperture is used to control the amount of light transmitted through the lens. Using the diaphragm, you adjust the size of the hole created by its petals in the inter-lens space of the lens. The wider the aperture, the stronger the luminous flux passing through the lens, and the better the camera is prepared for difficult situations with insufficient lighting. The aperture value (f /) is always represented as a decimal number, which decreases with increasing aperture diameter. For example, the aperture diameter at f / 2.0 is larger than at f / 2.8.

The effect of the diaphragm on the depth of field: f / 5

DOF wiggle aperture: f / 22

Different diameters of the diaphragm primarily affect the depth of the sharply depicted space (DOF). With small diameters, the depth of field grows, and all objects that fall into the frame are equally sharply depicted. With large values, the entire surrounding world becomes blurred, increasing the emphasis on the main object that has fallen into focus. A camera with a smaller aperture value (large relative diameter) is preferable for working in the dark and twilight when it is impossible or inadmissible to use additional artificial lighting. A tripod is undoubtedly a necessary tool for twilight and night shooting.

Shutter speed (exposure time)

So, we figured out that by changing the aperture, you can limit the amount of input light flux. But the camera also controls the time duration of the light flux for the correct exposure, that is, it determines the number of seconds required for a certain aperture value and a certain sensitivity. With a short shutter speed, the shutter will be open for exposure for hundredths of a second, which will allow the camera to “freeze” the movement of the subject. And with a duration of a second, all moving objects will leave a loop in the frame, which can be used as a technical technique that emphasizes the dynamics of what is happening. Excerpts, as a rule, have discrete values: for example, in the range from 15s to 1 / 2000s, these values ??will make up the series: 15s - 8s - 4s - 2s - 1s - 1/2 s - 1 / 4s - 1 / 8s - 1 / 16s - 1 / 30s - 1 / 45s - 1 / 90s - 1 / 160s - 1/320 s - 1 / 500s - 1 / 1000s - 1 / 2000s. However, some cameras may change smoothly.shutter speeds and are able to more accurately set the camera's operating parameters for proper exposure. With the same exposure value, the number of combinations of shutter speed and aperture can be more than a dozen. If your image is blurry, blurry or blurry, it means that a long exposure shutter speed was selected when shooting . To get rid of this fuzziness, you need to set a faster shutter speed or open the aperture.

ISO 100

ISO 400

ISO 800

Light Sensitivity (ISO)

The third parameter in determining the correct exposure is the photosensitivity of the photocell (film or sensor). The value of photosensitivity characterizes the ability of the photocell to perceive the light flux. Different ISO values ??suggest: for high sensitivity (ISO 400 or more units) - short exposure of the photocell, for low photosensitivity (ISO 100 units or less) - slow shutter speeds, at a constant aperture value. In most digital cameras, a high ISO value is always associated with strong digital noise, an analogue of film grain, and sometimes with a decrease in accurate color reproduction. This makes it more careful to choose the right photosensitivity.