The Nikon AF DX Fisheye-Nikkor 10.5mm f/2.8G ED ($774.95) is one of those lenses that's just a joy to use. When paired with a DX Nikon SLR, the svelte prime captures the world in front of it with a curved, fish-eye perspective. It can focus very close, produces crisp images, and features the build quality you expect from a Nikon lens. But it's not without some drawbacks, notably its price and the lack of autofocus support in entry-level SLRs like the D5500. There are less expensive alternatives out there, like the Samyang 8mm f/3.5 Fisheye ($279) and the Lensbaby Circular Fisheye, although the latter features a more extreme field of view that doesn't entirely fill the frame.

Design
The 10.5mm is a svelte lens, measuring about 2.5 by 2.5 inches (HD) and barely tipping the scales at a meager 10.8 ounces. The hood is integrated, and a slip-on cap protects both it and the bulbous front element. Because of the design of the lens, screw-in filters cannot be used. There's no stabilization system, but that's typical for a lens of this type—only a few ultra-wide zooms, like the AF-S Nikkor 16-35mm f/4G ED VR ($1,299.00 at Amazon) , feature optical stabilization.

The only control of which to speak is a manual focus ring. The lens does not include an internal focus motor, so it relies on your camera's screw-drive focus mechanism for autofocus. The current entry-level Nikon SLRs, the D3300 ($586.98 at Amazon) and D5500, don't include that mechanism, so the lens will only be useable with manual focus when mounted. You'll need to move up to the D7200 in order to have autofocus work. Switching between manual and automatic focus is done via the toggle switch on the camera body.

The lens is intended for use with APS-C (DX) SLRs. It can be mounted to a full-frame (FX) SLR, which can be set to automatically crop the active picture area to match that of the smaller DX sensor. Alternatively, you can set your FX to not crop in-camera, but that results in an image with a large black border. Some brave photographers have used tools to grind the hood away, converting the lens into a full-frame circular fish-eye.

The minimum focus distance is 5.5 inches (14 cm), measured from the image sensor. That means you can focus to about an inch from the front element. Close focus is often a strength of ultra-wide lenses, and with a fish-eye you can use it to creatively distort subjects.

Image Quality
We normally test lenses using Imatest and an SFRPlus test chart. Because of the extreme distortion a fish-eye delivers, it's not possible to evaluate its image quality from edge-to-edge using that setup, but I was able to get an idea of its sharpness at the center and middle third of the frame. Barrel distortion is heavy, about 27 percent, but that's to be expected.

At f/2.8 the lens scores 2,662 lines per picture height across the tested area when paired with the 20.9-megapixel D500 ($1,496.95 at Amazon) , a score that's better than the 1,800 lines we like to see in a photo. It improves as you stop down, peaking at 2,908 lines at f/5.6, and remaining strong at f/8 (2,831 lines), f/11 (2,672 lines), and f/16 (2,402 lines). You can stop down to f/22, but the score drops to 1,899 lines there.

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At narrow apertures the 7-blade diaphragm closes in a manner that turns bright points of light into stars. When you frame the sun in daytime shots it can be a stunning effect, and you can get the same look from streetlights and other bright sources of light in night shots.

I did notice some color fringing in images. It's evident at high contrast areas of the frame, where a bright sky meets a dark foreground subject, especially toward the edges. Thankfully, it's something that can be pretty easily removed with a software application like Lightroom ($9.99/Month at Adobe) , but if you don't like to spend a lot of time editing photos it's a concern.

Conclusions
It's not often that I think of a lens as especially fun to use—photography is an enjoyable hobby, but it's more about the experience than the tool used to get a shot. I'd say that the Nikon AF DX Fisheye-Nikkor 10.5mm f/2.8G ED is an exception. I found it to be creatively freeing, as I was more likely to shoot blindly from odd angles, trusting the autofocus to lock on to a subject, or to get up close to subjects that I'd normally capture from a greater distance. You may lose some of that freedom if you pair it with a camera with which it can't autofocus, but the focus throw is so short, it's easy enough to narrow the aperture a bit, set the focus mark to infinity, and fire away with aplomb.

Of course, you can also do that with a less expensive model, like the Samyang 8mm f/3.5 Fisheye—a lens we've yet to review, but will deliver a similar field of view on a DX Nikon SLR. Another option is the Lensbaby Circular Fisheye, but its more extreme field of view certainly differentiates it from the Nikkor. If you're in the market for a fish-eye lens, you should give the 10.5mm a serious look. It's on the pricey side, but it's an excellent performer, and the premium is certainly worth it if your camera has a screw-drive focus system.

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