The Teleconverter attaches between the lens and body to increase the focal length by a factor of 1.7. This provides a convenient way to expand your range of lenses. The Teleconverter 1.7 features the same outstanding optical and mechanical quality as all the lenses in the Hasselblad H1 system. Optical design is 6 elements in 4 groups.*Teleconverter is not compatible with the HC35 and HC50-110 Zoom.