Novices must learn how to expose photos correctly.

Novices must learn how to expose photos correctly.

We all know that to get a clear picture, we should not only be kind to Jiao Wai, but also make the exposure accurate and let the audience know what you want to express. However, when you first touch a digital camera, if you don't know how to expose it, you will encounter the following situations. The picture may be too dark when Sandy Lam sings, and then he will use a flash to brighten the picture. But it is very likely that the photos will be as bright as "flash bombs" or the light will be uneven. In order to put an end to this dilemma, let me explain to you how to make the photos exposed correctly!

Understand underexposure, precise exposure and overexposure.

Exposure refers to the process that the photosensitive element receives light and forms an image under certain conditions. Exposure is affected by shutter speed and aperture size (so-called exposure combination). There is no defined standard for exposure combination, and photographers need to arrange shutter speed and aperture size according to different shooting needs and picture effects. In general, accurate exposure can make the photosensitive element receive a relatively correct amount of light. However, underexposure will lead to the dark picture and the loss of dark details. But overexposure will make the picture too bright, and the details of the bright part will be lost.

F 1.4, 1/50s, focal length: 85mm, ISO 160.

Influence of photometry on photo exposure

Photometry is the process of shooting the scene exposure value at a designated position, which provides a reliable basis for accurate exposure. When a photographer uses a camera to measure light, the shutter, sensitivity and aperture will be combined into a exposure value combination. The camera will restore the subject to medium gray brightness for metering, but not all areas are completely medium gray brightness, so the photographer must choose the appropriate metering method and position. Only by accurate metering can the light and dark contrast of the picture be truly presented.

The high-speed shutter is used to shoot rivers and villages, and the aperture and sensitivity are adjusted accordingly according to the photometric results, so that the picture is rich in color and the magnificent scenery is accurately displayed. (F6.3,11250s, focal length: 200mm, ISO 320)

Set appropriate exposure compensation for the subject.

Exposure compensation is a way to control the exposure of a picture, and digital monocular cameras generally have exposure compensation function. When shooting some scenes, if the normal exposure can't accurately restore the color of the scene and let us get the ideal picture effect, then we can use exposure compensation to adjust the exposure. This function can be adjusted according to the needs of different scenes when shooting. When we shoot a snow scene, if we don't adjust the exposure compensation, the white in the picture will tend to be gray because of the reflective characteristics of snow. Therefore, after the photographer increases the first-level exposure compensation, the white color will be restored more accurately, and the correct snow scene can be better represented.

Exposure principle of "white plus black minus"

When shooting white or highlighted objects, in order to avoid the gray problem, the photographer will need to increase the exposure compensation appropriately. When shooting black objects or dark objects, it is necessary to appropriately reduce the exposure of the picture so that the dark details of the subject can be clearly presented. In these two pictures, we photographed the same cosmetic twice. The picture in the first picture is increased by 0.3EV exposure compensation, so it is really restored to white; The white in the second picture looks obviously gray and the color is distorted.

Method for calculating the value of flash lamp index GN

GN (derivative) is used to represent the flash index, that is, the light intensity of the flash. The greater the GN value, the greater the light intensity, and GN value = aperture coefficient x shooting distance. Therefore, it should be noted that with ISO value 100 as the standard, when we know the GN value and shooting distance, we can calculate the optimal aperture size according to the formula, which makes the shooting more accurate. Taking a flash with a GN value of 32 as an example, the exposure combination of shooting distance 2m and aperture F 16 will be equal to the exposure combination of shooting distance 4m and aperture F8.

Flash index: 32= F 16 (aperture) x2m (shooting distance) =F8 (aperture) x4m (shooting distance)

Relationship between flashlamp index GN value and exposure

Through the GN value, the photographer can also estimate the exposure for flash photography, because the original formula is GN value/shooting distance = aperture coefficient. In this way, we can choose to use the best aperture at different shooting distances to get the right picture exposure. The two photos were taken at the same distance, but the first one used the aperture of F2, and the picture was exposed enough. The other picture uses the aperture of F4, which is equivalent to reducing the GN value by half, so the picture is dark.

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