How many mm is the camera's lens length or lens diameter?
Lens focal length is the main performance indicators of the lens, its length determines the size of the shooting, the angle of the field size, depth of field size and perspective of the screen strength.
We often can see such a set of data on the lens, it is the focal length of the lens, if it is zoom lens, then the two groups of data is a section of the composition.
The number of mm marked on the camera lens is neither the length of the lens nor the lens diameter, it is the meaning of the lens to the focal point (focal plane) distance.
The focal length, also known as the focal length, is the measure of the aggregation or divergence range of the light in the optical system, specifically the distance from the center of the lens to the focus of the light gathering. Or from the lens optical center to the film, CCD or CMOS imaging plane of the distance. An optical system with a short focal length has better ability to collect light than a long focal length optical system.
The lens of the camera is a group of lenses that can be understood as a single lens. When the light parallel to the main optical axis through the group of lenses, converge to a point, this point is called the focus, the focus to the lens center (ie, the distance), known as the focal length. Focal length fixed lens, that is, fixed focus lens; focal length can adjust the change of the lens, that is, zoom lens.
The optical center of the lens, or the optical center, does not have a physical standard position, it can vary with the shape of the lens, even outside the lens.
Understand the meaning of the focal length, to master the camera perspective, composition, depth of field, and then shoot out the excellent works have important significance.
