optical zoom

The English name of the optical zoom is Optical Zoom. The digital camera relies on the optical lens structure for zooming. The digital camera's optical zoom mode is similar to that of a traditional 35mm camera. It is through the movement of the lens to zoom in and zoom out the scene that needs to be shot. The larger the optical zoom factor, the farther the scene can be shot.

When buying a digital camera, many users will ask, what is the digital zoom, what is the optical zoom, below, we use the graphic to explain.

Optical zoom is produced by changing the position of the lens, object, and focus. When the imaging plane moves in the horizontal direction, as shown in the figure below, the vision and focal length will change, and the farther scenes will become clearer, which will make people feel like objects are progressive.

Obviously, there are two ways to change the perspective. One is to change the focal length of the lens. In terms of photography, this is optical zoom. The focal length of the lens is changed by changing the relative position of each lens in the zoom lens. The other is to change the size of the imaging plane, that is, the length of the diagonal of the imaging plane. In current digital photography, this is called digital zoom. In fact, the digital zoom does not change the focal length of the lens, but only changes the angle of view by changing the angle of the image facing the corner line, thereby producing the effect of “equivalent to” the focal length change of the lens.

So we see that the longer the digital camera is, the larger the inner lens and the sensor are, so the zoom factor is even bigger. We see some ultra-thin digital cameras on the market, generally do not have optical zoom function, because the camera does not allow the movement of the photosensitive device in the root, but like the Sony F828, Fuji S7000 these "long lens" digital camera, optical zoom The function reaches 5, 6 times.

Today's digital cameras have optical zoom multiples of between 2x and 5x, which can bring objects closer than 10 meters to 5-3 meters; there are also some digital cameras with 10x optical zoom. The home camcorder has an optical zoom factor of 10 to 22 times, and it can clearly capture something 70 meters away. Using an extender can increase the camera's optical zoom factor. If the optical zoom factor is not enough, we can add a multiplier before the lens. The calculation method is as follows. A 2x teleconverter is placed on a digital camera with 4x optical zoom. The optical zoom factor of the camera is changed from 1x, 2x, 3x, and 4x to 2x, 4x, 6x, and 8x, that is, multiplied by the multiplier of the teleconverter and the optical zoom factor.