How to adjust the aperture size?

Aperture

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The size of the aperture is a parameter in the camera lens that controls light. To put it bluntly, the size of the aperture will determine the intensity of light passing through the lens. Therefore, you can easily imagine that the larger the aperture, the stronger the light projected through the lens onto the CCD sensor of the digital camera, and vice versa. Then its size will also directly affect the imaging quality of the digital photos we take. For example, when the shutter time is the same, the larger the aperture, the brighter the photo will be. If the aperture is too large, overexposure will occur. Regardless of whether it is a traditional camera or a digital camera, the aperture is represented by the letter "f", and the size of the central aperture of the aperture is represented by the corresponding numerical value, that is, "f + value". In use, it is worth noting that the smaller the aperture value, the larger the aperture of the aperture, and the more light will enter, and vice versa, the less light will enter. Therefore, when shooting, "increasing the aperture" usually refers to reducing the aperture value and enlarging the aperture. For example, go up one level from f5.6 to f4, or a higher level, f2.8, etc.

Shutter

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Shutter speed is also a parameter that controls the exposure time when taking photos. To make it easier for everyone to understand, we can also say that the shutter is the control time that allows the camera to maintain the currently set aperture size. The shutter speed is expressed using corresponding numbers, such as 1/4 second, 1/60 second, etc. They respectively represent the time to maintain the currently set aperture size for 1/30 second and 1/60 second. Therefore, it is not difficult to see that using different shutter parameters to maintain the length of time per unit aperture can also control the amount of light entering during shooting, that is, the exposure. The 1/30 second mentioned above is twice the time of 1/60 second. At this time, the amount of light passing through the unit aperture is also doubled, so in turn, 1/30 second is 1/15 second. In half the time, the amount of light passing through the unit aperture will be reduced by half. In actual shooting, we can achieve different effects by adjusting the shutter speed, such as a "river of cars" that looks flowing or solid water droplets, etc. They use slow shutter speeds and high (fast) shutter speeds respectively. realized.

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Aperture is the center of the camera lens The shutter is a mechanical device that can change the size of the middle hole. The shutter is a device (mechanical or electronic) that controls the length of the exposure time. The combination of the two can simultaneously control the exposure amount.

For example, light is like water flow, and the lens is like a hole with a gate that can control the direction and flow of water flow. Aperture is the size of the hole, and shutter is the time it takes to open.

When the gate opening time is fixed, the smaller the hole, the less water will flow in, and vice versa. When the shutter speed is constant, the aperture is appropriate (for example, f5.6), and the exposure is normal. If the aperture is too large (for example, f2.8), the photo is overexposed, and the photo (the developed positive film, not the negative film) will be white, without layers, or even A piece of white paper; if the aperture is too small (such as f11), the exposure will be insufficient, the photo will be dark, the low-light areas will be lost or even there will be no image.

When the size of the hole is constant, the longer the gate is open, the more water will flow in, and vice versa. Therefore, when the aperture is constant, the shutter speed is appropriate (for example, 1/250 second), and the exposure is normal. The fuller the shutter speed (for example, 1/60 second), the longer the exposure time will be, and the exposure will be overexposed, and the faster the shutter speed will be (for example, 1/1000 second). , underexposed.

It should be noted that although both aperture and shutter can control exposure, their functions are not equivalent. The smaller the aperture, the more concentrated the direction of the light. When it reaches the film (or CCD) for imaging, it is easier to obtain a clear image. (Of course, if the aperture is too small, diffraction will occur and become blurry.) The greater the depth of field, and vice versa. Therefore, when you need to precisely control the depth of field, you can first determine the aperture size and then the shutter speed. When shooting moving objects, if the shutter is open for too long, the moving objects will be imaged on different parts of the film (or CCD), and the photos taken will certainly not be clear. On the contrary, when the shutter speed is very fast, the moving objects will be imaged on the film. The image has not moved significantly, the exposure process has been completed, and the photo is clear, that is, the moving object is frozen on the screen. Therefore, when shooting moving objects, you can choose the fastest shutter speed as possible, and then adjust the aperture to correctly expose. Of course, if you want the moving objects to leave movement traces on the photo and enhance the sense of movement, you can choose a slower shutter speed.

Especially important is flash photography. Proper selection of shutter and aperture can well control the light ratio between flash and other light. Since the flash time of the widely used electronic flash is very short, only about one ten thousandth of a second, when the shutter speed is synchronized with it (the so-called synchronization means that the flash time falls in the time period after the shutter is fully opened and before it is closed) Otherwise, the shutter has not been fully opened when flashing, or it is already closing, and the flash will be meaningless. Even if part of the film is exposed and the shooting fails), extending the exposure time will have no effect.

Therefore, the effect of the flash is controlled by the aperture, and the effect of continuous ambient light (such as other lights in the night scene) is controlled by the shutter. Appropriate selection of exposure combinations can create perfect artistic effects.