Lan Hai Optics takes you to understand the type of zoom lens：

Depending on the focusing method, the zoom lens can be divided into manual zoom lens and automatic zoom lens.

Depending on the zoom range, generally speaking, 20-40mm is called a wide-angle zoom lens, 35-70mm is called a standard zoom lens, 70-200mm is called a medium and long zoom lens, and 200-500 is called a telephoto zoom lens.Of course, there are many lenses including wide-angle to medium-focal lengths, and even telephoto ranges, such as 28-200mm, 28-300 mm, and so on.

Depending on the zoom magnification, there are 2 times the zoom magnification (such as 35-70mm), 3 times, 5 times (28-135mm), 7 times (28-200mm), 10 times (50-500mm), etc. Generally, the larger the zoom range, the larger the volume, the lower the image quality, and the smaller the aperture.

Depending on the operation, it can be divided into push-pull zoom and rotary zoom.The advantage of push-pull zoom is that it is easy to use and can quickly zoom from the remote end to the near end.The disadvantage is that the lens is easy to slide when shooting down.The advantage of rotating zoom is that the focusing ring and the zoom ring are independent, and the rotating operation does not interfere with each other.But the operation is not as simple as push-pull, especially when using “zoom to shoot explosive effects”, it is not as simple as push-pull zoom.

Zoom lens function：

When focusing with a zoom lens, it is good to first focus the image to a large position; that is, to end the focusing with the long focal length of the lens.Then, reduce the focal length to the desired focal length when shooting.In this process, the image at all focal lengths is always clear.With this technology, because it focuses on the largest possible image, it is easier to observe whether the details of the image are clear, so it is also a precise focusing method.Note that some zoom lenses need to rotate two independent control rings, one for focusing and the other for focusing.