What Is a Teleconverter?

A teleconverter is also called a teleconverter. It is an optical accessory installed between the lens and the camera body. It is a lens accessory that extends the focal length to 2 or 1.4 times. First use a teleconverter on the lens. For example, if a 2X adapter is installed in a 100mm lens, the focal length becomes 200mm, and if a 1.4X adapter is installed, the focal length becomes 140mm. The price varies greatly depending on the manufacturer. The more famous the company's products, the more expensive it is.

Teleconverter

A teleconverter is also called a teleconverter. It is an optical accessory installed between the lens and the camera body. It is a lens accessory that extends the focal length to 2 or 1.4 times. First attach a teleconverter to the lens

A teleconverter is also called a teleconverter. It is an optical accessory installed between the lens and the camera body. It can enlarge the image.

Teleconverters have different amounts of magnification. A 2 × telephoto teleconverter can double the size of the image, that is, it can effectively double the focal length of the lens after it is installed. If a teleconverter is attached to a 50mm lens, the image obtained will be the same size as the image taken by a 100mm lens; if it is mounted on a 200mm lens, the image size produced by a 400mm lens will be obtained.

A 3 × telephoto teleconverter can triple the image size. It can effectively convert a 50mm lens into a 150mm lens and a 200mm lens into a 600mm lens.

Most teleconverters are quite small and affordable, so first of all we have addressed

When talking about the role of the teleconverter, we must first say

There are usually two types of teleconverters, one is 1.4x times and the other is 2x times. However, there have been many specifications recently. The first is a 3x teleconverter from a professional factory. Get unprecedented focal length, but

Teleconverters can make the focal length of our lenses longer, but there are sacrifices. One is sacrificed

Use between lenses

Today, 70-200mm and 70-300mm lenses have become very popular today. It doesn't make much sense to increase the focal length of 50mm, 85mm or even 135mm. By any means, using a lens with a focal length is always inconvenient. On the other hand, the original intention of using the focal length is to match the lens with a longer focal length. Usually, the focal length of the matching lens is longer than 50-100mm. The original focal length lens must be used with a longer focal length a lens. For example, Kengo teleconverters require that the focal length of the matching lens cannot be shorter than 50mm, and the short end of the zoom lens cannot be shorter than 50mm (it cannot match the lens with a diameter larger than F1.8). Its professional PRO300 is The focal length of the lens is required to be above 100mm. The shortest focal length lens that can be used with Canon EF2X and EF1.4X teleconverters is EF135mmf / 2L.

Note the shrinking aperture

The maximum aperture of the lens is not very good. If you shrink one stop, the image quality will be significantly improved. If you shrink two stops, you will get higher image quality. After the lens is equipped with a teleconverter, not only the aperture becomes smaller, but the image quality of the large aperture will be further reduced, and no small light will be received.

Teleconverter

It is difficult to guarantee the image quality when using the circle. Sigma has specially designed two professional teleconverters APOAF2XEX and APAF1.4EX for its APOAF70-200mmf / 2.8EX lens. Practice has proved that even if such a high-end professional lens is equipped with a special teleconverter, the image quality of the large aperture will decrease. After shrinking the aperture, the image quality will also be significantly improved. In principle, the focal length of 1.4X is not less than one stop, and the focal length of 2X is not less than two stops. There are very few large-aperture long-focal-length lenses in the hands of film friends, and most of them are zoom lenses. The aperture is generally f4-5.6. After double the focal length, the aperture becomes F8-11 (common aperture), which can be used in bright sunlight. Takes 1/125 seconds (set the film to the commonly used ISO100). If the aperture is reduced (it becomes f16-22), it will be difficult to use, and the exposure combination control will be limited. You can only extend the shutter stop, use a tripod, and cannot shoot the body. Therefore, for the sake of convenience, some film friends do not pay attention to the use of shrinking aperture, and can not get good image quality.

Use a fixed focal length lens to match

Usually, the fixed-focus lens has a larger aperture than the zoom lens, and the image quality is also better than that of the zoom lens. From the foregoing, it can be seen that this is obviously advantageous for ensuring the imaging quality and AF performance, and it is more convenient to use. At present, with the exception of the Canon EOS-3, the capabilities of AF systems in various factories are limited to AF performance at f5.6. In addition to several professional f2.8 constant large-aperture zoom lenses, the use of ordinary zoom lenses has increased. It is often difficult to guarantee the performance of AF after the focal length lens.

Choose high sensitivity

Setting the ISO value of the digital camera to a high sensitivity or using a high-sensitivity high-speed film can make up for

Teleconverter

The lens diameter lost after using the teleconverter lens can usually compensate for the aperture loss caused by the 1.5X teleconverter with ISO100 and ISO200, and the aperture loss caused by the 2X teleconverter with ISO400. With high-sensitivity film, the range of adjustable exposure combinations is increased, and the adaptability is enhanced.

Fifth, choose a solid large tripod

With a teleconverter, handheld shooting is often impossible. After the 70-200mm or 70-300mm lens is increased in focus, the long focal length will reach 500 to 600 mm. At this time, the stability problem of the camera will become very prominent, and even a small amount of shaking will cause the image to be blurred and cause shooting failure. At present, the tripods used by a considerable number of film friends are small and medium-sized, the quality of the process is poor, and there are many plastic parts.