Photography from zero to entry: understanding the three elements of exposure

Exposure is the core technique of photography, and exposure also contains very complex content.

Let me talk about exposure first. The core of photography is the use of light. The so-called exposure is to make the light appear on the photo correctly. In digital cameras, the principle of exposure is that the sensor converts the light signal into an electronic signal, but if we adjust the parameters incorrectly, we cannot get the correct information.

Sensitivity, aperture, shutter. The three elements of exposure check and balance each other, and one is indispensable. The three elements of exposure interact with each other, commonly known as the exposure triangle

Let’s talk about sensitivity first. Sensitivity is usually written as ISO, which is usually represented by numbers, such as ISO 100, ISO 200, ISO 12800, etc. Sensitivity represents the sensitivity of the camera to light. The higher the sensitivity, the more suitable for light shooting in dark environments.

Increasing the sensitivity can improve the ability to capture light, which is more suitable for shooting in dark environments

Although the higher the sensitivity, the more suitable for shooting in dark environments, but the higher the sensitivity, the greater the loss of image quality. Increasing the sensitivity will increase the noise of the photo, so in actual shooting, we should actually use a lower sensitivity as much as possible.

The shutter speed is directly related to the sensitivity. The main reason we adjust the sensitivity is to control the shutter speed. Every time the sensitivity value is doubled, the shutter speed can be doubled. So if we use low sense, such as ISO 100, the shutter speed will be slower, and use high sense will get a faster shutter speed.

Next, let’s talk about the shutter speed. The shutter speed is the exposure time, usually expressed in seconds. Normally, when shooting, the shutter speed is very fast, so it is 1/60 second, 1/200 second and so on.

The faster the shutter speed, the more suitable for shooting sports scenes. Generally, it takes more than 1/500s to shoot sports, more than 1/1000s for high-speed moving objects such as birds, and more than 1/2000s for sports racing cars and airplanes. In daily shooting, we generally control it at 1/60-1/200s.

If we shoot scenery and use a very slow shutter speed, such as the slow-door long exposure we often say, it can condense the sky, traffic, and pedestrians into silk. At this time we need more than 1 second of exposure.

Of course, the exposure time is directly related to stability. Usually we say that jitter will cause blurred photos because the shutter speed is not fast enough. Generally, the shutter speed must be higher than the reciprocal of the focal length. For example, if we use 100mm, the safety shutter is faster than 1/100s without anti-shake.

Shutter speed and exposure are also proportional. Each time the shutter speed doubles, for example, from 1/100s to 1/200s, the shutter time is reduced by half, and the exposure is reduced by half. If it changes from 1/100s to 1/50s , The exposure time is doubled and the brightness is doubled.

The last is the aperture, which is a more complicated parameter. Generally speaking, the meaning of aperture is the size of the clear aperture of the lens, which can represent the amount of light entering the lens (this statement is not accurate, but it can be understood as such). Half of the aperture is denoted by F, generally written as F1.4 or f/1.4. But the meaning of aperture is F=clear aperture/focal length, so apertures are all reciprocal, such as 1/8, 1/2.8, or 1:1.4.

Here you need to pay special attention. The aperture on the camera only displays the value. In fact, this is the denominator, so the smaller the value, the larger the aperture. f/1.4 is a large aperture, but f/14 is a small aperture.

The aperture is not increased by a multiple, but by the root number 2, which is approximately 1.4. So the gear positions of the aperture are: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22. In other words, it is not f/1.0 that is twice the aperture of f/2, but f/1.4.

The larger the aperture, the lower the sensitivity that we can use, or a faster shutter speed. But the larger the aperture, the shallower the depth of field of the photo, which is what we call the background blur. If we have the same sensitivity and a larger aperture, the shutter speed can be doubled, for example: ISO 100, shutter speed is 1/100s, aperture f/4, then aperture doubled to f/2.8, if ISO 100 does Change, the shutter speed can be increased to 1/200s; if the aperture is reduced to f/5.6, then the shutter speed will slow down to 1/50s.

Aperture mainly affects depth of field and exposure, that is to say, the priority of aperture adjustment is the highest among the three elements of exposure. We can adjust the aperture to control the shutter speed and the depth of field, which are the priority exposure factors in many subjects.

Usually we carry out exposure, first select the appropriate aperture and exposure speed, and then adjust the sensitivity according to the aperture and exposure speed, so as to obtain the appropriate exposure parameters. In fact, we don’t need to judge all the exposure parameters by ourselves, we only need to understand the influence of each exposure parameter, so that the camera can automatically determine the exposure value we need.

About Yalong

I like to write articles about digital products and digital life, and believe that it is these products that ultimately change people's lifestyles.

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