Is the Sony 20-70mm f/4 G the Do-Everything Zoom for the Mountains?

The Sony FE 24-50mm f/2.8 G and FE 20-70mm f/4 G both promise a smaller standard zoom, and each one asks you to give up something different to get there. If you carry a camera into the mountains for hours at a time, the choice between extra width, extra reach, and an extra stop of light shapes nearly every frame you bring home.

A standard 24-70mm f/2.8 is the safe default, and it's also the lens that starts to feel heavy around mile six. Mark Bergreen of The Bergreens took the Sony FE 24-50mm f/2.8 G and the Sony FE 20-70mm f/4 G on two climbing trips to see whether either could replace his Sigma 24-70mm f/2.8 DG DN Art. His checklist is short and demanding: 20mm on the wide end, at least 50mm and ideally 70mm on the long end, usable low-light performance, and a body small enough to hang from a shoulder strap all day. Image quality matters less here, since every contender produces excellent files.

Bergreen went in expecting to love the 24-50mm, and it disappointed him. You keep the constant f/2.8 aperture and lose 20mm of reach, and in exchange you should get a dramatically smaller lens. On the trail, the size difference felt smaller than the spec sheet suggests, and the price sits several hundred dollars above the Sigma. The 20-70mm f/4 played out differently. He's usually wary of f/4 zooms, but 20mm on the wide end kept saving him from swapping to a 16-35mm, and he describes it as carrying two lenses in one. The cost showed up at dawn and dusk, when f/4 pushed him as high as ISO 12,800.

The jump from 24mm to 20mm sounds small, but on a full frame camera, the horizontal field of view grows from roughly 74 degrees to about 84 degrees. That's enough to fit an entire ridgeline and a climber into one frame without backing up, which on a cliff edge may not be an option. The f/4 penalty has also shrunk in recent years. Since Lightroom added its AI-based Denoise feature in 2023, and similar tools arrived in other editors, a high-ISO raw file can be cleaned up far more than was possible when f/4 zooms earned their reputation as compromise lenses. One stop is still one stop, and you'll still give up some background blur. But if most of your wide shots are landscapes stopped down for depth of field anyway, the extra width is something you'll use on far more frames than the extra light.

Bergreen also runs through the wider field of mid-range zooms, including the Sony FE 24-70mm f/2.8 GM II, which costs close to twice as much as the Sigma, and the Sony FE 28-70mm f/2 GM, a lens he admires for its rendering but wouldn't want to haul up a mountain. He points out that the 4mm gap between 24mm and 28mm matters more in daily use than it looks, especially indoors, and that dropping to 28mm saves a surprising amount of weight. Then, as he was wrapping up the video, Sigma announced the Sigma 20-60mm f/2.8-4 DG Contemporary. Variable apertures complicate manual exposure, since zooming in can leave you a stop underexposed unless you adjust, and he doesn't yet know where in the zoom range the aperture shifts from f/2.8 to f/4.

Bergreen's verdict on which zoom he's actually buying is in the video above.