Zoom lens is also a type of lens that can change the focal length without changing the lens. The zoom lens has a varying focal length. Nowadays, the optical industry uses computers to design lenses, and many excellent zoom lenses have been manufactured. Many zoom lenses produce very clear images and are also compact in size.
Zoom lens is a camera lens that can change the focal length within a certain range, thereby obtaining different field of view widths, different sizes of images, and different ranges of scenery. The zoom lens can change the shooting range by changing the focal length without changing the shooting distance, which is very advantageous for composition. Since a zoom lens can take on the function of several fixed-focus lenses, it not only reduces the number of photography equipment carried when traveling, but also saves the time of changing lenses.
The zoom lens is divided into box-type lens and portable lens according to the external size of the camera lens. Theoretically, the lens of the box-type lens is larger, and its optical characteristics are stronger than those of the portable lens. The focal length adjustment and focusing of the box-type lens can only be performed by the focus and zoom servo handle, while the zoom and focus of the portable lens can be selected through the switch on the lens for manual or servo operation.
When using the zoom lens for focusing, it is best to consider first adjusting the image to the maximum and then focusing; that is, using the longest focal length of the lens for focusing. Then, reduce the focal length to the expected focal length when shooting. During this process, all images at various focal lengths are always kept clear. Using this technique, because focusing is done under the maximum possible image, it is easier to observe whether the image details are clear, and therefore it is the most accurate focusing method.
Note that some zoom lenses require the rotation of two separate control rings, with one ring controlling the focus and the other ring controlling the focal length. The advantage of this structural layout is that once the focus is completed, the focus point will not be accidentally changed by adjusting the focal length. Other zoom lenses only require the movement of one control ring, rotating it for focusing, and sliding it back and forth to change the focal length. This "single-ring" zoom lens is often faster and more convenient for operation, but it is usually more expensive. It should be noted that when changing the focal length, do not lose the clear focus.