Why a full-frame lens on an APS-C body?

Why would you put a full-frame lens (FX in Nikon terminology) on an APS-C (DX) body? With such a lens, you then use, after all, only the inner half of the image circle. You still have to deal with the weight – and not to forget the price – of a full-frame lens. Even so, there are three reasons to consider this FX lens for a DX body as well:

1. FX lenses are, as a rule, superior in terms of image quality. After all, they are intended for sensors with a whole lot of pixels. Because with a DX body you only use the middle of the image circle, flaws such as distortion will be reduced, and vignetting and edge blur will even be largely eliminated.
2. In the second place, you have, if you later switch from DX, on FX format, the certainty that you can keep using your “old” lenses.
3. In addition, there are not many DX lenses with brightness like this f/1.8.

Build and auto focus

The lens has a plastic housing; this ensures low weight (ca. 300 g) and reduces costs. The high brightness has advantages in low light but is primarily intended for the creation of nicely blurred backgrounds. You can ‘free’ your subject from the background. The use of plastic makes the lens – at least in theory – more prone to incidental front focus/back focus (as a consequence of thermal expansion) and somewhat more fragile that with an entirely metal housing. There is a broad rubber focus ring and a window that shows the distance set. With a switch, you select MF or M/A, in which case you focus automatically but can still turn ‘through the focal point’ by hand.
An advantage of a bright lens is that the automatic focusing happens faster and, as a rule, more precisely. When focusing by hand, a limited amount of ‘play’ was noticeable. This is a disadvantage when you want to photograph while zoomed in via Live View on your LCD screen (or connected laptop or tablet).

Vignetting Nikon 28mm f/1.8G

There is some vignetting in the corners at full aperture, about three-quarters of a stop. This is barely visible in practice shots, as shown in this picture of a clear sky.

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Distortion

In the JPEG mode, the distortion will be immediately corrected by the camera. In RAW, there is some (-0.8%; 30% lower than on an FX camera) distortion visible. Distortion is simple to correct with software, at the expense of a little bit of corner sharpness.

Flare

Sharpness

Nikon AF-S 28mm f/1.8 G & D7100 @ f/5.6, 1/640 sec, 100 ISO
You see no distortion here, but skew because the photographer was not standing directly in front of the subject and held the camera at an angle.

Chromatic aberration

Bokeh Nikon 28mm f/1.8G

The bokeh (the quality of the blur) can be called fine with this lens. That comes from, among other things, the 7 rounded aperture lamellae. This is also an advantage of FX lenses above DX: they typically have more aperture lamellae because there’s more space in the lens housing. From the just-visible onion-ring pattern, it can be seen that there are 2 aspherical lenses applied in the design of the Nikon 28 mm 1.8G.

Conclusion Nikon AF-S 28mm f/1.8 G test with Nikon D7100

WYSIWYG score: This table shows the performance of this lens if you save the files in the camera as jpg, where you have applied all available in-camera lens corrections. This score gives you for this lens/test camera combination: “What you see is what you get”. 

testcamera: Nikon D7100

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Pure RAW score: This table shows the performance of this lens if the file is saved in the camera as a RAW file. This score approaches the intrinsic quality of the combination of lens and test camera.

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Pros

Cons

• High image quality
• High brightness
• No/very little flare
• Fine bokeh

• Larger, heavier and more expensive than a DX lens

This Nikon 28 mm f/1.8 is an attractive lens with very good resolution and a reasonable price/quality ratio. Of the 22 lenses that we have reviewed with a focal point between 23 mm and 30 mm, the Nikon 28 mm f/1.8G lands in the top 5, regardless of whether you’re looking at a jpg file (incl. in-camera corrections and standard sharpening) or a RAW file (without sharpening or corrections). Is this then the ideal documentary lens for a Nikon photographer with a DX camera? There are after all multiple, although less bright, zoom lenses that offer equally good image quality at this focal length. And the Sigma 18-35 mm f/1.8 not only has the same brightness, but is at least as good qualitatively. On the other hand, the Sigma 18-35 mm cannot be used on a (future) camera with an FX sensor. You also mustn’t underestimage the pleasure that many photographers experience with a fixed focal length. As far as that’s concerned, the Nikon 28 mm f/1.8G is clearly the ideal 35 mm lens for a DX camera.