What is the meaning of high light ratio in photography?

Light ratio is one of the important parameters of photography, which refers to the ratio of the brightness of the light receiving surface to the brightness of the shadow surface of the object being photographed.

Under the distribution of natural light and artificial light, the brightness of the light-receiving surface of the object is high, and although the shadow surface does not receive light directly (or less), it still has a certain brightness due to scattered light (or auxiliary light). The light ratio is often expressed in the form of "light receiving surface brightness/shadow surface brightness".

Light ratio also refers to the ratio of brightness of adjacent parts of an object and the contrast between light and shade of the main part of the object. Large light ratio, large contrast, small light ratio and small contrast. The light ratio determines the contrast between light and shade of the picture, forming different light and shade and tone.

Direct light tends to form a large light ratio, and scattered light tends to form a small light ratio.

Extended data

Light ratio measurement

The light ratio can be measured by external exposure meter, and the light and dark parts can be measured by incident photometry. The light ratio can be calculated by comparing the aperture values.

If the light exposure meter reads F 1 1 and the dark part reads F8, the light ratio is1:2 when the shutter and sensitivity are measured twice. The bright reading is F 1 1, the dark reading is F5.6, and the light ratio is 1: 4. The law is 1: 2 (aperture difference). More than one aperture and less than two apertures are generally defined as 1: 3. This is the most commonly used illumination ratio in portrait photography.

You can also use the camera's spot metering function and reflection metering to measure the light ratio. After measuring the bright and dark parts, calculate the aperture level difference as above. But pay attention to white plus black minus.

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