Focusing principle of camera lens

The focal length is the same as that of the human eye. Digital cameras capture everything in the world through the lens. If the human eye has an error (myopia) in the focal length, it can't distinguish things correctly. As the lens of a digital camera, its most important characteristic is also the focal length of the lens. The focal length of the lens is different, the breadth of the scene that can be shot is different, and the photo effect is also very different.

If you often use an ordinary 35 mm camera, you should have a basic understanding of the focal length of the camera lens. For example, you usually take scenery and commemorative photos with a lens of about 35 mm, and take photos with a lens of about 80 mm to identify the "big head" you need.

Compared with traditional cameras, because digital cameras use CCD photosensitive devices, the focal lengths indicated on their lenses are usually 5.0 mm, 10 mm, etc. In ordinary 35 mm cameras, super wide-angle or fisheye lens is generally used, while the lens commonly used by digital camera manufacturers is only a small wide-angle lens equivalent to 35 mm cameras.

Extended data

Influencing factors:

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

2, focal length, the longer the focal length, the smaller the depth of field; The shorter the focal length, the greater the depth of field. This is why the focal lengths of 85mm and 70-200mm are suitable for portraits, because the blur is good. This is also the reason why the mobile phone cannot be blurred, because the equivalent focal length of the mobile phone is below 20 mm (the blurring of two lenses is an algorithm, not optics).

3, focusing distance, other conditions being the same, the closer the focus, the smaller the depth of field.

4, camera frame, the larger the frame, the smaller the depth of field. This is one of the reasons why Quan Huafu is superior to the remnants.