Tamron has announced the development of a 70-300mm F/4.5-6.3 Di III RXD lens for Sony full-frame mirrorless cameras. 

The new telephoto zoom will join several other focal lengths in Tamron's Sony E mount lineup including the 17-28mm F/2.8 Di III RXD, 28-75mm F2.8 Di III RXD, and the 28-200mm F2.8-5.6 Di III RXD. Tamron says the 70-300mm will have a length of 5.8 in. and a maximum diameter of 77mm while weighing 19.2 oz, making it one of the most compact 300mm telephoto lenses available. 

Similar to other RXD models, it will have a moisture-resistant construction and a 67mm filter thread for accessories. The lens is also expected to be compatible with the Hybrid AF and Eye AF found on Sony's Alpha models that include the new a7S III thanks to its fast stepping motor. Though a 70-300mm lens is generally looked to for sports and wildlife photography or capturing the rare comet, using long lenses for films can produce images with an entirely different look and feel. Cinematographer Darius Khondji used long lenses in Uncut Gems exceptionally well. 

Tamron didn't release much about the lens, but it's safe to say it will follow the same design principles of other lenses in its class –  low dispersion elements, circular aperture, fluorine coatings, and a lock button on the barrel. However, the company will be celebrating its 70th Anniversary this November, so maybe shooters could see deals down the line.