What is a multiplier?

Rangefinder, also known as telephoto zoom lens, is an optical accessory installed between the lens and the camera body. It can enlarge the image. Telescopes have different magnifications. A 2-time telephoto lens can double the image, that is, the focal length can be effectively doubled after the lens is installed. If the telephoto lens is attached to the 50mm lens, the image obtained will be the same size as that taken by the 100mm lens; If it is installed on a 200mm lens, you will get the image size produced by a 400mm lens, and so on. A three-fold telephoto lens can enlarge the image three times. It can effectively convert a 50 mm lens into a 150 mm lens and a 200 mm lens into a 600 mm lens. Most telephoto lenses are quite compact and moderately priced, so first solve the two problems of telephoto lenses mentioned above-expensive and bulky. So, why don't you buy a telephoto lens instead of the bulky and expensive one? The reason is that the rangefinder has lost its original image quality; In other words, the image is not as clear as that obtained by a telephoto lens with the same focal length and quality. However, don't be disappointed, the level of telephoto lens is improving every year. A few years ago, the products still lacked the advanced optical system necessary for clear imaging, but today's telephoto lens is characterized by multi-unit lens structure and high quality. Therefore, using high-quality modern telephoto lenses loses much less image quality than in the past. Therefore, according to the advantages of price and convenience, you can decide whether to make limited concessions on acceptable image quality, although we warned at the New York Institute of Photography that we should persistently pursue the perfect image quality as possible. However, we also admit that sometimes photographers have to face the reality. Supplement to the use of telephoto rangefinder: After studying exposure in detail in Unit 2, we will understand that telephoto rangefinder can reduce the film arrival. If the exposure meter through the lens is used, which is the common type of exposure meter in most single-lens reflex cameras, then exposure compensation is not needed. Because the exposure meter has automatically taken into account the reduced amount of light. The same is true if you use the "automatic exposure mode" of a camera that measures light through the lens. However, if you use a separate exposure meter, such as a hand-held exposure meter, you must compensate for the lost light. The compensation amount is as follows: for 2 times telephoto range extender, open two apertures, for 3 times telephoto range extender, open three apertures, and so on. The use rate of rangefinder in shooting activities is relatively low, and many people still hold a sneering attitude towards using it. They think that the use of rangefinder will greatly reduce the imaging quality, and the effective aperture will become smaller, which will affect the framing and focusing. Some test reports in magazines also advocate this. I admit that the use of rangefinder will have the above shortcomings, but if you are not a perfectionist, but pay more attention to the content of the work or emphasize that the work should reflect your own ideas, you will find that rangefinder still has many advantages. For example, we ordinary enthusiasts sometimes want to shoot some lotus flowers in the pond, birds in the trees, and a bigger sun ... The zoom lens with the longest focal length of 200 ~ 300 mm always feels out of reach in our hands. If we add a folding telescope lens made in Europe, it will increase the burden on our shoulders, and the macro function is poor (compared with using a range extender) and you don't specialize in shooting one. Might as well add a small rangefinder. No, even professionals occasionally use it: Guan Tianhao's photo of Wang wearing a five-star red flag after winning the Atlanta Olympic Games was named "See the Fairy Flying again" and won the first prize of the news group in the 4th Asian Style Chinese Film Competition. It was shot with a 600mm lens and a zoom lens of 1.4 times. More enthusiasts use two range extenders at the same time, and the sun is really big and beautiful. In this way, the telephoto lens can not only solve people's urgent needs, but also satisfy the desire of enthusiasts to "overlook", which is really not small! Since the rangefinder has such advantages, I have higher expectations for it. I've been thinking about whether I can have a better multifunctional rangefinder, and I've gradually got some ideas in my heart. I also want to send a suggestion to Canon and Nikon on the Internet on a whim, so that they can adopt my suggestion and produce my imaginary rangefinder. But I learned from some magazines that the rangefinders of Canon and Nikon have great limitations in use, and they are only suitable for replacing some lenses in the lens group (it is a special product specially designed for professionals, how can we design a "one-vote" rangefinder for poor enthusiasts like us)? There are too many business opportunities hidden in the design and production of manufacturers, which left us, and I immediately dismissed this idea. Recently, I learned from the photography department that Longteng Company has introduced a new 2x zoom lens, which can not only be used for all lenses, but also automatically focus when the effective aperture is reduced. This is a zoom lens designed for our fans. Although I gave up the idea of making suggestions, I was still full of ideas.