Sony 100-400mm f/4.5 GM: The Case for Constant Aperture in Sports Photography

Sony’s updated 100-400mm G Master keeps the focal range and changes almost everything else — most significantly the aperture, which is now a constant f/4.5 across the entire zoom range rather than the f/4.5-5.6 variable of the original, making the lens two-thirds of a stop faster at the long end precisely when sports and wildlife photographers need it most.

Why Constant Aperture Matters at Telephoto Ranges

Variable aperture telephoto zooms make a practical compromise: the lens is smaller and lighter when extended, but the maximum aperture narrows as you zoom in. On the original Sony 100-400mm, reaching 400mm meant working with f/5.6 — manageable in bright conditions, limiting in the early morning or overcast light where wildlife activity peaks. Shooters using autofocus tracking at 400mm f/5.6 were working with less light than the same focal length on a constant-aperture lens, affecting both exposure flexibility and phase-detect autofocus reliability.

The updated lens resolves this with a constant f/4.5 across the full 100-400mm range, an inner-zoom design that doesn’t physically extend as it zooms (unlike the original, which grew longer toward 400mm), and 11 aperture blades instead of 9 — improving background separation quality at the same time. The tradeoff is weight: the lens comes in at 1,840g (4.06 lbs) versus the original’s 1,495g.

The Autofocus and Optics Upgrades

Sony claims autofocus speed up to three times faster and subject tracking up to 50 percent better compared to the previous version, driven by four XD Linear Motors that replace the dual-motor system of the original. For sports photographers shooting action at 400mm with Sony’s AI subject recognition, that tracking improvement matters more than the raw speed claim — sustained lock across erratic motion is the harder problem.

On the optical side, Sony redesigned the lens formula using ED XA (Extra-low Dispersion Extreme Aspherical) elements to suppress chromatic aberration while minimizing onion-ring bokeh, a fringing artifact that affects background rendering on complex aspherical lens designs. The result, according to The Phoblographer’s early testing, is “exceptional resolution across the entire focal length range” with cleaner separation than the first generation.

Minimum focus distance is 0.64m at 100mm and 1.5m at 400mm, enabling 0.25x maximum magnification — practical for insect photography and tight wildlife compositions that benefit from close-focus capability on a long telephoto.

Source: PetaPixel

Content created with AI assistance and reviewed for accuracy.