Sigma AF 100-400mm f/5.6-6.3 DG DN OS

The Sigma 100-400mm f/5.6-6.3 DG DN OS gives you 400mm of reach with solid stabilization at a fraction of the Sony GM price. The slow aperture and lack of weather sealing are the main compromises. Worth buying if you shoot wildlife or sports in decent light and want to save money and weight.

Reach is the star here. At 400mm on a full-frame body, this lens sits in the 91st percentile for focal length coverage, which puts it in the top tier for wildlife and sports framing. Stabilization is also a standout, landing in the 89th percentile, so handheld shots at the long end are more forgiving than you'd expect from a lens this light. But the aperture is a real limitation. At f/5.6-6.3, it ranks in the bottom 6% of all lenses in our database, which means you'll be cranking ISO or dropping shutter speed once the light fades. Autofocus is middle of the pack, and bokeh is nothing to write home about. Sharp enough for the price, but not a low-light hero.

Against the Sony 100-400mm GM, the Sigma loses on aperture, build, and autofocus speed, but wins on weight and price. The Sony is the better lens, full stop, but it's also heavier and costs a lot more. The Nikon Z 70-200mm f/2.8 VR S and Canon RF 24-105mm f/2.8 are different beasts entirely, faster and sharper but with far less reach and much higher price tags. The Tamron 35mm f/1.4 and Viltrox 35mm f/1.2 aren't even in the same category. If you need 400mm on a budget, the Sigma is the pragmatic pick.

At around $1,000 USD, this lens is a solid deal for the reach you get. Sony's own 100-400mm costs significantly more, and while it's sharper and faster, the Sigma gets you 90% of the way for a lot less cash. The affordability score sits in the 32nd percentile, so it's not a screaming bargain, but for a full-frame 400mm zoom with stabilization, the price is fair. If you're patient, used copies pop up for less, which makes it even more tempting.

The Sigma 100-400mm f/5.6-6.3 DG DN OS is a telephoto zoom built for full-frame mirrorless shooters who want serious reach without carrying a brick. At 1098g, it's noticeably lighter than Sony's own 100-400mm, and that's the whole pitch here. You get 400mm of reach, optical stabilization, and a price that undercuts the first-party option by a wide margin.

But there are trade-offs. The aperture is slow at f/5.6-6.3, there's no weather sealing, and the build feels more budget than premium. For wildlife and sports shooters on a budget, it's a compelling option. For low-light work or rough conditions, you'll feel the compromises.

Skip this if you shoot in low light, bad weather, or need fast autofocus for action. The f/5.6-6.3 aperture and lack of weather sealing will frustrate you. If you're a pro who needs the absolute sharpest images or shoots in rain and dust, save up for the Sony GM or look at a faster prime.

This lens is for wildlife and sports shooters who want long reach without spending Sony GM money or carrying a three-pound lens. It's a great travel telephoto for daylight shooting. If you shoot in low light, need weather sealing, or demand fast autofocus, this isn't your lens. But for the price, it's hard to beat the reach-to-weight ratio.