Therefore a 50mm becomes a 100mm or a 135mm becomes a 270mm lens. Keep in mind that in doubling the focal length you are also "losing" 2 f/stops. So a 50mm f/1.4 becomes a 100mm f/2.8 or a 135 mm f/2.8 becomes a 170mm f/5.6. Therefore I would only recommend using this with "faster" lenses.
This device also makes a great close-up or macro device, because the closest focusing distance of your lens remains the same, but the image size is magnified 2 times.
It comes with the original leather case and front and rear lens caps.
This will work with all manual focus SLR film cameras that use the M42 screw mount.This includes Pentax, Mamiya, Yashica, Practica, and others. It has the "auto" feature to maintain the auto diaphragm feature of your camera and lenses.
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