SMC Pentax-DA 300mm F4 ED IF SDM Telephoto Lens Pentax Lenses K mount 21760. The SMC Pentax-DA* 300mm F4 ED [IF] SDM is a prime telephoto lens with a fast quiet autofocus drive bright aperture compact design and multiple coatings for excellent sports and wildlife results.. Pentax. 21760. 027075141261