Optics: 10 elements in 9 groups. Traditional spherical design, multicoated. Traditional front-group focusing. In terms of video autofocus, the Sigma 28-70mm DG DN has the potential to be a really great option. Not only does it offer silent autofocus drive and very nicely-damped manual focus, but it also has well controlled focus breathing. There's only a bit at the 28mm wide-angle end and very little at all by the time you zoom in to 70mm. It's aimed at photographers and videographers who want a bright walkaround zoom and the bokeh possibilities that a wide aperture brings but who don't want the size, weight and cost typical of many F2.8 zooms. Travel and landscape photographers in particular will find its modest size and weight appealing, and it also offers potential as a portrait lens or for video capture. For the most part, bokeh is very pleasing, with only very slight onion ring and a nice, polygon-free shape even when stopped down to F4. 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.

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.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. When it comes to distortion, we need to discuss the Leica L-mount and Sony E-mount versions of the lens separately. That's because if you're an L-mount shooter, distortion is corrected automatically in both JPEG and Raw files, but if you're shooting Raw on the E mount variant on a Sony body and using Adobe software, there's (currently) no correction applied for distortion. Distortion isn't an issue for the L-mount version thanks to automatic correction, but Sony E-mount variants show some barrel distortion at wide-angle and prominent pincushion at telephoto. 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.

Proper fraction button is used to change a number of the form of 9/5 to the form of 1 4/5. A proper fraction is a fraction where the numerator (top number) is less than the denominator (bottom number). There's just a little bit of longitudinal chromatic aberration, visible as color fringing, around high contrast edges of slightly out-of-focus regions, but as you can see in the sample below, it's not really anything to concern yourself over. It disappears immediately upon stopping down. 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. Sunstars are relatively pleasing, with 18 rays thanks to the nine aperture blades. They're not as tight as they could be – each ray splits and diverges into two rays – and as expected stars on the wide end look better than those on the telephoto end where they can appear a bit 'messy'.Up front, you'll find 67mm filter threads. That's the same size as used by its Tamron rival, while the Sigma 24-70mm F2.8 opts instead for a larger 82mm filter thread. A little bit of longitudinal chromatic aberration can be seen as magenta and cyan color fringing around high contrast edges in the image above. It's subtle enough to be a non-issue for the most part, and goes away as you stop down the lens. There's both good news and bad news on the bokeh front. The Sigma 28-70mm F2.8 DG DN's bokeh has a really pleasing, smooth look to it, with only minimal onion ring effect and smoothly-rounded, step-free edges even when stopped down to F4.

Sure, it has some caveats in the image quality department. Most notably, corner sharpness isn't stellar at telephoto while wide-open; close-up telephoto shots wide open can have a soft dreamy look , and it's also quite prone to cat's eye bokeh effect. But honestly, depending on your subjects, those may not be major concerns for you. And image quality is otherwise solid, with very good sharpness across much of the focal range, pleasing bokeh, and good resistance to aberrations and ghosting. This 35-70mm f/3.5 AI was Nikon's first professional midrange zoom from 1977. It is very sharp at every setting and has a constant f/3.5 aperture. It has less distortion than any of Nikon's f/2.8 zooms, and that means much better than the 24-70mm AF-S and 28-70mm AF-S, each of which costs over ten times as much. 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. See Nikon Lens Compatibility for details on your camera. Read down the "AI, AI-s" column for this lens. We didn't see any major issues with lateral chromatic aberration for this lens. There's a truly minute amount of it, perhaps 2-3 pixels wide on a 42MP image (that's a half a millimeter on a 40" x 60" print) that clears up easily if you enable CA corrections in-camera or in your Raw converter.

Stopping down to F5.6, we see a slight improvement in sharpness at wide-angle and a bigger improvement at telephoto, since the lens is softer wide open at 70mm than it is at 28mm. You'll appreciate this improvement in sharpness more if you're shooting with a high-resolution camera. We tested with both the 42-megapixel Sony A7R III and 47-megapixel Panasonic S1R; with a 24-megapixel body, that difference would be much less noticeable. Cat's eye effect is quite noticeable when shooting wide-open and can appear quite a long way towards the center of the image frame. And since it is so lightweight, balance is very good. Regardless of the mount variant you choose, it shouldn't feel front-heavy on any body you might want to pair it with. 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. Vignetting is not a concern for the Sigma 28-70mm F2.8. It's only really noticeable at telephoto, and even there is minor and easily corrected. Bokeh

NIkon made a 43-86mm f/3.5 zoom before this, but since it is neither a normal zoom (43-86mm is normal to tele), and since it was never pitched as a professional zoom, I'm not counting it as Nikon's first pro normal zoom. The 43-86mm was a convenience zoom, not a zoom with which to earn one's living. Life is all about compromises. With a bright, continuous aperture and minimal size and weight being the key elements of its design, it's not surprising at all that the Sigma 28-70mm F2.8 DG DN's image quality can't quite compete with larger, more expensive alternatives like Sigma's own 24-70mm F2.8 DG DN Art. On the telephoto end the maximum magnification ratio is 0.22x. Close-up subjects shot at 70mm can appear soft and dreamy. 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.

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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. The Nikon 35-70mm f/3.5 AI zooms by moving the elements inside the barrel. Nothing moves externally except the zoom ring. Roll your mouse over to see what happens. I moved the focus a little between shots; pay attention not to the focus ring but to the glass which is moving up and down. 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.