No.6 x 2.75 (3.5mm x 70mm) TX Countersunk Self-Tapping Screw - Stainless Steel (A2) (Pack of 20)

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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. 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. 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.

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. 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. If you can take your time, the newer 35-70mm f/3.5 AI-s lens is even better optically, although I find this AI version easier to focus.

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'. On the telephoto end the maximum magnification ratio is 0.22x. Close-up subjects shot at 70mm can appear soft and dreamy. 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. 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.

Results at 70mm follow a similar pattern, but with softer results overall, particularly at close focus distances. Wide open, portraits can often look a little dreamy.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. Production History: The 35-70mm f/3.5 AI was introduced in 1977 and built until it was replaced by the 35-70mm f/3.5 AI-s in 1981. Nikon made about 50,000 of these AI versions.

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. 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. 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. 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.

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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. 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. 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. 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. 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.