What is depth of field? What are the factors affecting the depth of field? How many ways are there to measure light? How many kinds of lenses are commonly used?

Depth of field refers to the distance range of an object measured along the axis of an imager, which can obtain a clear image in front of a camera lens or other imager.

Influencing factors: (1), lens aperture:

The larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field;

(2), the lens focal length

The longer the focal length of the lens, the smaller the depth of field; The shorter the focal length, the greater the depth of field;

(3), shooting distance

The farther the distance, the greater the depth of field; The closer the distance, the smaller the depth of field.

Photometric method: At present, the photometric methods adopted by the camera are different according to the measuring area of the photometric element, mainly including point photometry, central part photometry, center key average photometry, average photometry mode, multi-zone photometry and so on.

Spot metering mode: the metering element only measures a small range in the center of the picture. When shooting, the camera lens is aimed at various parts of the subject many times and its brightness is measured one by one. Finally, the photographer determines the exposure parameters according to the measured data.

Central part metering mode: This mode measures the central area of the picture, accounting for about 12% of the picture.

Central focus average metering mode: This mode takes the center of the picture (about 60% of the picture) as the focus, taking into account the edge of the picture. It can greatly reduce the phenomenon of poor picture exposure and is the main metering method of SLR cameras at present.

Average metering mode: measures the average brightness of the whole picture, which is suitable for the situation that the light intensity of the picture is not much different.

Multi-area metering mode: the picture is metered by independent metering elements in different areas, and the data is processed by the microprocessor inside the camera to obtain appropriate exposure with high exposure accuracy. Backlight photography or when the contrast of the scene is large, appropriate exposure can be obtained without manual correction. Reasonable, get appropriate exposure and high exposure accuracy. Proper exposure can be obtained when backlight photography or scene contrast is large, and manual correction is not needed.

Lens type:

One: standard lens

A standard lens is a lens whose focal length is close to the diagonal length of the camera frame.

Two: wide-angle and ultra-wide-angle lenses

Third; Telephoto and ultra telephoto lenses

Fourth; Fisheye lens and reflective lens

Five; zoom lens

Six; Special lens

The commonly used special lens is macro lens; Angle adjusting lens; Soft focus lens; And a zoom additional mirror.

Seven; Image stabilization lens