If you prioritize outright image quality and durability over size, weight and cost, we'd recommend the fully weather-sealed Sigma 24-70mm F2.8 DG DN Art. And for E-mount shooters who are more size, weight and cost-conscious but who need to shoot regardless of the elements, the Tamron 28–75mm F/2.8 Di III RXD also offers a compelling alternative if you can live with its more distracting bokeh. As a two-ring zoom it's best for use on a tripod. Hand-held, I constantly need to grab zoom, then focus, then zoom, then focus, etc. I can't do both at once as I can with a one-touch zoom.

The 35-70mm f/3.5 AI is a great lens for film and FX Digital. It's silly for DX digital because there are far more modern DX lenses that do a much more convenient job. So if I have to augment the 28-70 with two additional lenses, I might as well save weight/space and gain capability with a single prime. The 35-70mm f/3.5 AI is a masterpiece of precision. You have to feel one to appreciate it. The focus flips with a fingertip from 3 feet (1m) to infinity. All the zoom action happens inside the barrel: the front and rear groups move around inside the barrel while the exterior doesn't move at all. But if what you need most of all is portability and you understand the compromises necessary to achieve it, the Sigma 28-70mm F2.8 DG DN is hands-down the smallest and lightest of the bunch and still offers solid image quality.

Comments

Shooting wide-open at F2.8 (which you'll quite likely want to spend much of your time doing if you've bought this lens for its bright maximum aperture), sharpness is very acceptable in the center of the frame at 28mm and remains pretty good even once you zoom in to the 70mm telephoto. Focal Length: 35-70mm. Used on a DX camera it gives angles of view similar to what a 50-105mm lens would give on an FX or 35mm film camera. See also Crop Factor. Distortion isn't an issue for the L-mount version thanks to automatic correction, but the Sony E-mount variant shows some barrel distortion at wide-angle and quite prominent pincushion at telephoto. This lens is a joy to use. It just works, never gets in the way, and yields great results. Just be careful not to let the sun shine into it for fear of veiling flare. So when does a zoom make sense? When it covers more than one easily discernable FL. But 28-70 doesn't do that. It has a single useful perspective for me. A "normal" perspective. I would need to augment it on both sides with a lens that is wider and a lens that is more tele.

It doesn't hurt that it's also among the most affordable F2.8 full-frame standard zoom options for the E- or L-mounts. For the size, weight and cost-conscious, it's definitely worthy of consideration.

Converters

Sharpness drops off a little at the corners on the wide end at F2.8, but stopping down to F5.6 gives a relatively flat field of focus and improved corner sharpness. That said, focusing in the corner yields higher corner sharpness than focusing in the center and stopping down, indicating a curved field of focus. Focusing in the corner and stopping down yields even better corner sharpness, as expected. The not-so-flat field of focus, at least in part, contributes to the peripheral softness when focusing centrally. Compatibility: On the D2, D3, D200, D300 and F6, use the "Non-CPU Lens Data" menu option to input the zoom setting and f/3.5, which will give you full matrix metering and EXIF data, and finder read-out of set aperture. It works great in aperture-preferred as well as manual modes on these cameras. As you might expect, the featherweight Sigma 28-70mm F2.8's body is predominantly constructed from polycarbonate, although it does still have a metal mount and build quality is good. And while it isn't fully weather-sealed like its nearest rivals, the mount still includes a seal that should help protect your camera body from the elements, if not the lens itself.