Large depth of field photo parameters

The topic involves two issues: depth of field and night scene shooting.

There are only three factors that affect the depth of field: aperture, object distance and focal length.

First, the aperture

In the case of constant focal length and object distance: the larger the aperture, the smaller the depth of field; The smaller the aperture, the wider the depth of field.

However, when the aperture is small to a certain value, diffraction will occur and the image quality will be reduced. It is generally not recommended to use the smallest two-step aperture.

Second, the object distance

Object distance is the distance from the subject. When the aperture and focal length are fixed, the closer the object distance is, the smaller the depth of field is. The farther the object distance is, the wider the range of depth of field is.

Third, the focal length.

When the aperture and object distance are constant: the longer the focal length, the smaller the depth of field; The shorter the focal length, the wider the range of depth of field.

Tips. The focal length will change the perspective relationship of the picture, and reasonable application can change the perspective relationship between the front and rear objects and a single object.

Depth of field is inversely proportional to aperture, inversely proportional to focal length and directly proportional to object distance.

It is also worth noting that the depth of field behind the focus is twice that of the foreground. So when taking several rows of big photos, you will focus on the first third of the line (for example, when taking four rows of people, you should focus on the face in the second row). Similarly, when shooting the scenery of a big scene, you can focus on the first third of the main building complex.

When applied to your night scene creation, because the focal length is unchanged, in order to get the effect of large depth of field, you can reduce the aperture to the range of 8- 16, and get a larger depth of field on the basis of ensuring the image quality; Greater depth of field can also be obtained by patterning away from the subject.

How to Accurately Expose Night Scene Shooting

How much exposure is needed mainly depends on the light intensity of the environment. The automatic metering of the camera is basically very accurate and can be used for reference.

The sensitivity is generally controlled between 200-400, which will not produce too much noise, and the aperture is generally controlled between 8- 16, which can ensure the imaging quality on the basis of ensuring a large depth of field. At this time, the shutter speed often does not exceed 15s. A tripod will be another necessary tool.

On the basis of this time, we can shoot tracks.

There are many tips for shooting night scenes:

Blue light moment: There is a beautiful moment to shoot the night scene: after sunset 15-30 minutes, the color of the sky will gradually change from light yellow to warm yellow, and then the night scene will be blue until it is completely black. The period when the sky is blue is also called blue moment. The blue light of the sky and the warm yellow light of the city can form a beautiful contrast between cold and warm.

Shake black card: commonly used when the light ratio is quite different. Photographers first measure the light in bright and dark areas respectively, and remember their shutter speed. Then, they cover the bright area with black cardboard and shake it slightly. First, they expose dark areas. When the exposure time of dark areas is close to the time difference between them, they quickly pull out the black card and let the bright areas begin to be exposed. When bright areas are exposed normally, they close the shutter. Photos taken in this way will be more realistic in HDR and cheaper than installing gradient lenses.