Good focal length lenses with five issues

· Good focal length lenses with five issues first, increase the focal length lenses with long focal length lenses. In 70-70-210mm and has become a very popular 300mm lens, we give 50mm, increasing the focal length 135mm 85mm and even has little significance. No matter from which side, use additional focal length of the lens is not convenient. On the other hand, using the original intention of increasing the focal length is also used with focal length · good focal length lenses for five questions first, to increase the focal length lenses with long focal length lenses. In 70-70-210mm and has become a very popular 300mm lens, we give 50mm, increasing the focal length 135mm 85mm and even has little significance. No matter from which side, use additional focal length of the lens is not convenient. On the other hand, using the original intention of increasing the focal length is longer with the focal length of lens, typically required to match the lens focal length is longer than 50-100mm, original plant of focal length lenses to cope with a longer focal length lens. For example, Ken high (Kenko) increase the focal length lens requires corresponding matching of the lens focus can not be shorter than 50mm, zoom lens of the short-end cannot be shorter than 50mm (also cannot match the diameter > F1.8 lens), its professional PRO-300 requires 100 mm lens focal length. Canon EOS with additional focal length EF1.4X EF2X, mirror the most able to tie in with the short focus lens is EF135mm f/2L · good focal length lenses with five issues second, note the contraction of the aperture. We know that the lens of maximum aperture imaging are not very good, shrink a retaining the aperture, the image quality will be improved significantly, the contraction of two retaining can achieve higher image quality. Lens with focal length lens, increasing not only the aperture smaller, larger aperture image quality will further decline, not-to-use small aperture is very difficult to guarantee the image quality. Shima company specifically for its f/APO AF70-200mm 2.8EX lens designed two professional additional focal length lens APO AF2XEX and APAF1.4EX, practice has shown that even such high-end professional lens with focal length lens, dedicated to increasing large aperture image quality may deteriorate, shrinking the aperture after image quality will be improved. In principle, increasing the focal length 1.4X shrinkage aperture one stop use, increase the focal length 2X contraction, not less than 2 retaining the aperture. Fans in the hands of the very few large aperture telephoto zoom lens, and the zoom lens, the caliber is f4-5.6. 2 multiply the focal length, Aperture becomes F8-11 (commonly used Aperture), shooting in bright daylight could use 1/125 sec shooting (set of film as popular ISO100). To shrink the aperture (become f16-22), it is very difficult to use a combination of regulation and control, exposure limits, you can only extend the shutter, and tripod, and cannot be flapping. Therefore, some fans in order to facilitate, not paying attention to shrink the aperture, you don't get good image quality. Third, with a fixed focal length lens. Usually fixed focal length lens diameter is larger than the zoom lens, the image quality is also better than zoom lenses, by foregoing know it to guarantee the image quality and AF performance clearly beneficial, it is more convenient to use. Currently, in addition to the Canon EOS-3, the plant's ability to AF system limited to ≥ f5.6 AF performance when you can play, in addition to several professional constant f2.8 large aperture zoom lens, a normal zoom lens equipped with additional focal length lenses are often difficult to guarantee the future performance of AF. Fourth, select high speed film. High speed film can make use of additional focal length lenses after loss of lens aperture, ISO100, ISO200 usually used to compensate for the additional focal length 1.5X bore losses, ISO400, can make up for the additional focal length 2X bore the loss. Use a high speed film, adjustable exposure combination range increases, adaptive capacity enhancement. The current high speed film grain or rough, the price is high, as a last resort, consider using again. · Good focal length lenses with five issues fifth, choose solid large tripod. With increase in focal length lens, handheld shots often become impossible. 70-70-300mm 200mm or increase the focal length lens focal length end up after long wuliubai mm when the camera stability problems become very prominent, just a little bit of wiggle will cause ambiguity, causing the shot image failed. At present, a considerable number of fans using a tripod is small and medium-sized, process quality is poor, plastic parts, no stability, it is difficult to meet with the increasing focus of Coke (long focal length).