1 Fixed focal length: The focal length is fixed and can be divided into two types: with aperture and without aperture.
· With aperture: The size of the lens aperture can be adjusted. According to the changes in ambient light, the size of the aperture should be adjusted accordingly. The size of the aperture can be adjusted manually or automatically. The aperture is manually adjusted by humans, which is called manual aperture; the lens with a built-in micro motor to automatically adjust the aperture is called automatic aperture.
· No aperture: That is, the aperture is fixed, and its light transmission is fixed. It is mainly used when the light source is constant or the camera has its own electronic shutter.
2 Variable focal length: The focal length can be adjusted as needed to enlarge or reduce the image of the object being photographed.
Commonly used zoom lenses are six times and ten times zoom.
Three variable lenses: adjustable focal length, adjustable focus, and adjustable aperture.
Two variable lenses: adjustable focal length, adjustable focus, and automatic aperture.