How to use the aperture correctly in photography?

Aperture, also known as aperture diaphragm, is used to change the aperture size to control the luminous flux of the imaging carrier. In 1939, Frenchman Martin invented the automatic aperture of the camera. The size of the aperture affects the luminous flux. The so-called luminous flux is the amount of light passing through the lens. The unit of luminous flux is Lumen, 1 Lumen = 1 foot candle. The luminous flux multiplied by the exposure time equals the amount of exposure. Specifically, the limiting luminous flux is a component in the aperture called the "pupil." Aperture is a bionic technology of the human eye, just like a pupil (light intensity needs to be reduced, and light intensity needs to be enlarged). The pupil can limit the area of ​​incident light. The size and position of the pupil determine the illuminance and clarity of the image.

The aperture can not only control the luminous flux, but also control the depth of field. The larger the aperture, the smaller the depth of field, and the smaller the image clarity range; the smaller the aperture, the larger the depth of field, the larger the image clarity range. Not only that, the aperture can also control the image quality. A large aperture means a large aberration; a small aperture means a small aberration. In addition, light will scatter when passing through small holes or edges of objects. This phenomenon is also called diffraction. The smaller the aperture, the more serious the diffraction phenomenon.

It is worth noting that the aberration increases with the opening of the aperture, and the diffraction becomes more serious as the aperture decreases. The key is the right of two evils, which should be the lesser one.

So how to set the aperture?

• Set the aperture with light or dark. Use a small aperture for strong light, and a large aperture for weak light; when meeting the needs of light and darkness, you need to consider whether the shutter speed is allowed and whether the sensitivity is optimized. Because the factor that determines the correct exposure is the exposure combination (aperture size, shutter speed, sensitivity size), not just one of them.

• Set the aperture as required by the depth of field. A large aperture can blur the background and highlight the subject; a small aperture can achieve a large depth of field, which is suitable for shooting scenery. The best aperture in the medium aperture has the relatively best imaging quality, which is suitable for subjects with medium depth of field requirements.

• Set the aperture with the image quality. Use the best aperture and its neighboring aperture more often, and use less or less the limit aperture. The imaging quality is relatively worst because of the extreme aperture.

• Set the aperture according to the focal length. The focal length of the lens becomes longer, the light travel will naturally lengthen, and the light intensity and illuminance will inevitably attenuate. Generally speaking, the longer the focal length, the better to use a large aperture (the depth of field will decrease); the shorter the focal length, the better to use a small aperture (the depth of field will increase).

• Set the aperture with creative intent. The combination of aperture, shutter speed and ISO sensitivity should be optimized according to the creative intention to obtain satisfactory exposure and achieve the purpose of creation.

• Set the aperture based on shooting experience. Suggest you: F16 for strong sunlight, F11 for thin clouds covering the sun, F8 for cloudy weather, F5.6 for cloudy days, and F4-F2.8-F2-F1.4 for indoor lighting at night.

 

The above are general experiences or rules, but rules are not impossible to break. We encourage everyone to have the courage to continuously innovate and keep trial and error in photography practice, so that your photography skills can continue to improve.