Small format camera focal lengths ranging from 200 mm to 2000 mm. The use of these objectives requires the tripod.
Teleconverters and doublers of focal
They are not targets themselves, but are converters, adapters that are inserted between a target and the camera body to change the lens focal length. It is a cheap way of doubling the focal length, while remaining light and image quality. The brightness varies by about twice the proportion in which they alter the focal length. Thus a target 50mm f: 2.8, with a x2 doubler becomes a 100mm f: 5.6. There duplicators from x1, 3 x1, 5, x1, 7, to x2.