Tamron SP Flat Field 1.4x Teleconverter (Model 01F) is a compact, five element optical wonder that increase the focal length and magnification ratios of your Tamron Adaptall lens by 1.4x. Designed to fit your lens and Tamron adaptall mount, full AE or TTL capabilities of your camera are maintained. The flat field optical design uses high dispersion and features a doublet combined with an air spaced double concave lens for creating the magnification effect. The rear doublet minimizes magnification effect and serves to flatten the field and correct off-axis aberrations. Superior performance is achieved with the flat field converter, on- and off-axis