Nikon camera lens focal length
When it is the lens of the camera, it becomes the clearest as the general does not just fall on the focus, or, the clearest, Generally not equal to the focal length, but slightly larger than the focal length. The specific distance is related to the distance between the illuminated object and the lens (object distance), the larger the object distance, the smaller the distance (but in fact it is always greater than the focal length). Because we are photographed, the distance between the illuminated object and the camera (lens) is not always the same, such as giving a photo, sometimes, like the whole body, away from the body, away from the body, away from the nearest. In other words, the distance is not always fixed, so that in order to get a clear image, it must be different with the object to change the film to the lens of the distance, the process of change is that we usually say " Coke ".
Some of the camera is very stressed that with a 1 cm proximity to support the magic, suitable for shooting fine objects. The lens of the camera is a group of lenses, when parallel to the main optical axis of the light through the lens, it will gather to a little, this point is called the focus, focus to the center of the lens 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. (When a bundle of parallel light passes through the convex lens with the convex lens through the convex lens, the other side of the convex lens is converged by the convex lens, which is called the focal point, and the focal point to the convex lens center distance is called the focal length of the convex lens. There is a focus on each side.) Optical center (Optical center): a special point in the lens, all through the point of light, its propagation direction unchanged. The lens of the camera we use is equivalent to a convex lens, where the film (or the photographic device of the digital camera) is in the vicinity of the focus of the convex lens, or the distance between the film and the convex lens is approximately equal to the focal length of the convex lens. The focal lens of the convex lens can be imaged, usually with a lens of the lens of the camera.
Introduction to the physical concept of focal length If you read the camera in the English specifications "f =", then the back of the digital is usually its focal length, that is, the length of the focal length. Such as: "f = 8-24mm, 38-115mm (35mm equivalent)", refers to the length of the camera's focal length of 8-24mm, while the diagonal angle of the equivalent of the traditional 35mm camera 38-115mm The In general, 35mm camera lens lens length is about 28-70mm, so if the focal length is higher than 70mm on behalf of the support for telephoto effect, if less than 28mm said there is wide-angle shooting ability. "Focus range" is the extension of the focal length, usually divided into the general shooting distance and close distance, the camera's general shooting distance are usually marked as "from a centimeter to infinity", and near-stage design of the product is often also Will provide close-up shooting function (macro), to make up for the general shooting mode can not focus on the problem.
