The Nikon AF-S DX Nikkor 18-300mm f/3.5-6.3G ED VR ($699.95) dangles the promise of an extremely long zoom range in front of photographers, making it appealing to shutterbugs looking to minimize lens changes or pack light for a vacation. Its build quality is solid, as you'd expect from Nikon, but its asking price is on the high side and image quality is very disappointing when zoomed past 200mm. It'd be a little easier to recommend at a lower price, but at $700 it's not too much of a stretch to opt for Nikon's pricier, far superior AF-S DX Nikkor 18-300mm f/3.5-5.6G ED VR instead.

Design

The 18-300mm follows the design paradigm of every other modern Nikkor zoom. Its barrel is black polycarbonate with gold accents, and both the zoom ring and manual focus ring have a textured finish. The lens measures 3.9 by 3.1 inches (HD), weighs 1.2 pounds, and supports 67mm front filters. It's smaller than the pricier 18-300mm f/3.5-5.6G, which comes in at 4.7 by 3.3 inches, weighs 1.8 pounds, and has a larger 77mm front element.

A hood isn't included—Nikon's HB-39 shade is a $35.50 add-on—so I didn't use one in testing. Like other lenses of this type, the 18-300mm extends when zoomed, just about doubling in length at 300mm. To get an idea of the zoom range, take a look at the image above, shot at the widest angle, and the one below, at 300mm, captured from the same position.

You can mount the lens on a full-frame camera like the D610 ($732.97 at Walmart) , but you'll see a dark vignette surrounding the image in your viewfinder, and the photos you take will be automatically cropped to match the APS-C sensor size. The crop factor is about 1.5x, giving the lens a field of view that's closer to what a 27-450mm full-frame lens would deliver. On an APS-C camera the image circle covers the sensor and viewfinder.

The zoom ring has marked settings for 18, 35, 70, 105, 200, and 300mm. There's a lock switch that keeps the zoom set at its shortest 18mm setting, useful for times when your camera is at your side and you don't want gravity to cause the barrel to creep out. There's an A/M setting to switch between automatic and manual focus, and an On/Off switch to control the Vibration Reduction (VR) system.

The minimum focus distance is 1.6 feet (48.8cm), even at 300mm. This gives the zoom a strong 1:3.1 magnification factor—at the closest focus distance and maximum zoom it projects objects onto the image sensor at about one-third life-size. Competing lenses, including the Nikkor 18-300mm f/3.5-5.6G and Sigma 18-300mm F3.5-6.3 DC Macro OS HSM Contemporary ($398.20 at Amazon) , also focus this close.

Image Quality

I tested the 18-300mmm with the 24MP Nikon D5600 SLR. At 18mm f/3.5 the lens scores 2,107 lines per picture height on Imatest's standard center-weighted sharpness test. Image quality is above the 1,800 lines we want to see at a minimum through most of the frame, although edges are noticeably blurry, showing just 1,235 lines.

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Stopping down to f/4 bumps the overall score slightly to 2,271 lines, but doesn't do much for the edges. If you want photos that are crisp throughout the frame, stop down to f/5.6, where the average score is 2,548 lines and edges show 1,900 lines. At f/8 the lens is a strong performer, showing 3,111 lines across the frame with a sharp 2,665-line score at the periphery of the frame. Peak performance is at f/11 (3,534 lines), and while you can get good results at f/16 (3,109 lines), you should avoid f/22 as narrowing the iris that far diffracts light and drops the score to 2,163 lines.

At 35mm the maximum aperture has dropped to f/4.2. Results are a little bit better than at 18mm—2,318 lines—but edges are still a problem area, showing just 1,337 lines. Narrowing the aperture to f/5.6 nets better average performance (2,449 lines) and edges (1,718 lines). Again, f/8 is where you want to be. The average score improves to 3,089 lines, which carries through most of the frame, with edges that hit 2,500 lines. Peak performance is again at f/11, 3,545 lines, with crisp quality from edge to edge. The expected drop in fidelity is apparent at f/16 (3,155 lines) and f/22 (2,417 lines). The lens performs in the same manner at 70mm.

At 105mm the f-stop has dropped to f/5.6, and while the average score is still solid (2,204 lines), edges remain a problem area (1,246 lines). Stopping down to f/8 doesn't do quite as much good here as it does at wider settings—the average is a solid 2,545 lines, but edges are still on the soft side (1,676 lines). You'll need to stop down to f/11 in order to capture images with excellent quality throughout the frame—2,844 lines on average with 2,300-line edges. At this setting, f/16 is the peak f-stop, with a 3,031-line score, and f/22 isn't that bad (2,548 lines). You can narrow the aperture further if desired; f/29 is available, but it's not recommended.

It's at 200mm where image quality drops significantly. At f/6 the average score is 1,596 lines, which nets photos with noticeable softness. Edges are dismal, 820 lines. Stopping down to f/8 only improves the average score to 2,090 lines, but the periphery is still below 1,000 lines. It's not until f/11 where the lens is a truly solid performer, showing 2,714 lines and 1,771-line edges that are reasonable for a zoom lens. For excellent performance across the entirety of the frame stop down to f/16, where we see 2,771 lines on average with edges that lag just behind. The score drops to 2,393 lines at f/22.

Photos are even softer at 300mm f/6.3, at 1,376 lines. Only the center third of the frame is better than 1,800 lines. The mid parts show just 1,190 lines and edges 723 lines. There's improvement at f/8, but aside from the central third of the image, you get soft results. The average score is 1,763 lines, with the center crisp at 2,341 lines, the mid parts on the soft side at 1,609 lines, and blurry 838-line edges.

Results are much better at f/11—2,482 lines on average, with strong performance through most of the frame and soft, but not terrible, 1,552-line edges. Photos are crisp throughout the entirety of the frame at f/16 thanks to a 2,620-line average score. Performance is also decent at f/22 (2,349 lines), but you shouldn't stop down further—there's no reason to shoot at f/32.

The larger, pricier 18-300mm f/3.5-5.6G puts up better numbers when zoomed. It has some issues with the periphery of the frame at its maximum aperture at longer focal lengths—that's to be expected for such a long zoom—but it nets a 2,305-line average at 200mm and 2,122 lines at 300mm, both wide open at f/5.6.

Like its more expensive sibling, the 18-300mm f/3.5-6.3G does show some distortion throughout its zoom range. There's significant barrel distortion, 4.8 percent, at 18mm, which gives photos a mild fish-eye look. Lines bend the other way, inward, when zoomed in a bit. There's about 2.3 percent pincushion distortion from 35 through 70mm, 2 percent at 105mm, 1.8 percent at 200mm, and 1.5 percent at 300mm. If you shoot in Raw format you'll want to apply distortion correction in software—Adobe Lightroom CC includes a profile for one-click corrections. If you opt for JPG capture you can enable automatic in-camera correction, but be aware that you'll lose some picture information at the edges of the frame, so what you see in the optical viewfinder won't perfectly match with the finished image.

Imatest also analyzes images to determine if illumination is even across the frame. I use an Expodisc to shoot a flat gray frame and analyze it with the software's Uniformity tool. Corners are dim at 18mm, lagging behind the center by about 2 stops (-2EV) at f/3.5 and f/4. Stopping down to f/5.6 cuts the difference to -1.3EV, and at f/8 the illumination is within our -1EV tolerance.

At 35mm illumination is fairly even from corner to corner. But at longer focal lengths we see about a -1.5EV drop when the lens is shot at its widest f-stop. Narrowing the aperture to the next full-stop setting brings peripheral illumination within tolerances. Like distortion, you can correct illumination using a lens profile in Lightroom for Raw capture, and JPG shooters have the option of enabling automatic in-camera correction, so some corner dimness isn't a major issue.

Conclusions

Nobody expects a zoom with as ambitious of a range as the Nikon AF-S DX Nikkor 18-300mm f/3.5-6.3G ED VR to be an impeccable optical performer. Issues like distortion are readily removed, either in-camera or via software, but there's no fixing a lack of detail. We expect some softness at the edges of the frame—even an excellent long zoom like the AF-S DX Nikkor 18-300mm f/3.5-5.6G ED VR shows some—but such weak overall performance when zoomed to the telephoto range isn't something you want in a superzoom lens, let alone one that's priced at $700.

If you want a long zoom lens for your Nikon SLR, spend the extra $300 on the f/3.5-5.6G ED VR version. If that's too much, consider the Sigma 18-200mm F3.5-6.3 DC Macro OS HSM Contemporary as a solid, affordable alternative at just $400. Nikon also has its own 18-200mm, the AF-S DX Nikkor 18-200mm f/3.5-5.6G ED VR II, for $650, but we've not yet had a chance to test it.

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