Superlative G Master quality in the world's lightest1 600mm F4.0 lens uses two XD (extreme dynamic) Linear Motorsfor fast precise autofocus to take full advantage of the world's fastest cameras2 - reaching speeds up to 20fps with the 24MP α9 and up to 10fps with the 42.4MP α7R III and 24.2MP α7 III. 1 Compared to 600mm F2.8 lenses for 35mm full-frame format cameras, as of June 2019, Sony survey. 2 Fastest in their class. Referring to Sony's 35mm full-frame E-mount cameras, a9 at 20fps, a7R III at 42.4MP at 10fps. According to Sony tests.