Brief introduction of rangefinder

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 50mm lens into a 150mm lens and a 200mm lens into a 600mm lens.

Most telephoto extenders are quite compact and moderately priced, so we first solved two problems of telephoto lenses-expensive and bulky. So, why don't you buy a range extender to replace the bulky and expensive telephoto lens? The reason is that the rangefinder has lost its original image quality; In other words, the image is not as clear as 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, these products still lacked the advanced optical system needed for clear imaging. The current telephoto lens is characterized by a high-quality multi-unit lens structure. Therefore, using high-quality modern telephoto lenses loses much less image quality than in the past. So you can decide whether to make limited concessions on acceptable image quality according to the advantages of price and convenience. But we also admit that sometimes photographers have to face reality.

Supplement to the use of telephoto lens: After studying overexposure in detail in Unit 2, we know that telephoto lens can reduce the film arrival. If the exposure meter through the lens is used, which is a common type of exposure meter in most single-lens reflex cameras, then there is no need for exposure compensation, because the exposure meter has automatically considered the reduced light input. The same is true if you use the automatic exposure mode of a camera that measures light through a 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 rangefinder, open two apertures, for 3 times telephoto rangefinder, open three apertures, and so on.