Nikon 50mm f/1.8
By Jim Tanner

Center Sharpness
The DxO Blur Plots from the main review page and Figure 1 below display considerable information about the Sharpness of the Nikon 50mm f/1.8 lens itself and how it performs relative to the six lenses we included in this 50mm shootout. As you move the vertical slide on the blur plot from its lowest position (f/1.8) to its highest (f/22), you see that the Nikon f/1.8 images start (f/1.8) slightly soft (2-3 blur units) with the corners even softer than the center, and then steadily both flatten and get sharper until f/5.6, where the plot is very flat (no corner softness) and very sharp. This (flat, sharp) performance continues through f/11. Diffraction effects begin to degrade the image for f/16-22. In other words, you get the best (overall sharpness) images in the range f/4-11 (a comfortable range for "sweetness").

Figure 1. Center Sharpness: Nikon 50mm f/1.8 versus Six-Lens Average

Now, more about Figure 1 which depicts (in purple) the center-frame sharpness for the Nikon f/1.8 over its full aperture range. Also shown (in black) is a plot of the group average (of the six lenses employed in this review) blur value for the aperture range (f/1.2-f/45) spanned by the six lenses included in this shootout. The group average is shown at apertures where data is available from two or more lenses (f1.4-/22). While the Group Average is below that of the Nikon f/1.8 over the great majority of the aperture range, the differences are small (0.1-0.3 blur units) and real-life images by the Nikon and "the six-lens composite" would appear (sharpness-wise) essentially identical, even under close scrutiny. In fact, DxO asserts that blur differences of less than 1 blur unit are usually not discernible by the average observer. Over this aperture range the f/1.8 lens has an average blur factor of 1.35 blur units against a group average of 1.26. This is a very good center sharpness performance for a lens with a street cost of about $115.

Corner Sharpness
As we remarked earlier, the DxO Blur Plots show substantial corner softness for f/1.8 and f/2.

Figure 2. Corner Sharpness: Nikon 50mm f/1.8 versus Six-Lens Average

This is verified in Figure 2, which plots curves of the Corner Sharpness measured for both the Nikon 50mm f/1.8 lens and the group average. This "moderate softness" is, in fact, better than the corner softness exhibited by the group average. From f/2.8 though f/22, the corner performances by the Nikon and the "six-lens composite" are essentially identical. The six-lens average for this aperture range is 2.4 blur units while the Nikon f/1.8 average is 2.2 blur units; again, a visually imperceptible difference.

Chromatic Aberration
The DxO Chromatic Aberration plot shows the Maximum and Average Chromatic Aberration for the Nikon 50mm f/1.8 over the full aperture range of the lens. There is nothing particularly noteworthy about the data; that is, there are no unusual swings or noticeably high values over the full spectrum.

Figure 3. Chromatic Aberration: Nikon 50mm f/1.8 versus Six-Lens Average

The two purple curves of Figure 3 depict the same data shown in the graph we just discussed. The black curves of Figure 3 show the group maximum CA and average CA at each of the nine apertures in the f/1.8-f/22 range. Clearly, the Nikon f/1.8 performs pretty much on par for wider apertures and shows an improving trend (absolutely and relative to the group results) over the remainder of the aperture range. Over this range the Nikon average values of (max = 3.6, avg = 1.7) are below the group values (max = 4.0, avg = 2.1). To summarize, the Nikon 50mm f/1.8 lens has a slightly better than average Chromatic Aberration performance relative to its competitors.

Shading (Vignetting)
The DxO Shading (Light Falloff, Vignetting) graph indicates an initial (f/1.8) Shading slightly less than 0.4 EV which falls rapidly through the lens aperture range (f/1.8-f/22) to a fairly constant value less than 0.1 EV. There's little, if anything unusual here.

Figure 4. Shading: Nikon 50mm f/1.8 versus Six-Lens Average

The purple curve of Figure 4 repeats the DxO graph and adds the group performance. Over this range (f/1.8-22) the group average is 0.15 EV while the Nikon f/1.8 has an average value of 0.22 EV. While the other five lenses in the shootout have lower (better) Shading performances than the Nikon 50mm f/1.8, this is an acceptable Shading performance by the Nikon f/1.8, and from f/2.8 on, the differences are all but imperceptible.

Distortion
DxO Analyzer performs two measurements for distortion by a lens, the Maximum Distortion and the Average Distortion over the entire frame. The Nikon f/1.8 has very low values (max = 0.04%, avg = 0.02%) relative to the group values (max = 0.14%, avg = 0.06%). Only one lens (Sigma 50mm f/2.8) has better distortion values than the Nikon 50mm f/1.8.

AF Operation
On the D200, the Nikon f/1.8 focuses quite rapidly (less than a second) form infinity to closest focus (about 40 cm). At closest focus on the 1.5x crop factor D200, the width covered by the frame about 15 cm. The lens is a bit noisy when focusing, but not distractingly so. Unlike the Canon f/1.8, this lens does have a distance scale and the manual ring is wide enough to use without difficulty. Low-light focusing is quite acceptable. The (minimum) aperture must be set to f/22 and locked with the lever on the top right of the lens before the AF will function though. The AF/M choice is made on the body of the camera.

Build Quality and Handling
The Nikon f/1.8 is a small, very light lens which appears to be constructed almost entirely of plastic, apart from the lens elements themselves. Even so, it feels reasonably sturdy in one's hand and displays no unsavory looseness. The Nikon 50mm f/1.8 relies on the camera body to drive its lens elements during autofocus. (That is, it doesn't sport one of Nikon's excellent AF-S in-lens ultrasonic motors.) A consequence of this is that manual focus won't function when the lens/camera is in the AF mode.

The Competition
The Table below summarizes the performance of the six lenses over the (f/2.8-f/16) aperture range, the largest range that is common to all six lenses in the shootout. In a later report, we will expand this table graphically by showing the full-aperture-range performance for each lens against each other lens for Center Sharpness, Corner Sharpness, Chromatic Aberration, and Shading. This will be a total of 60 graphs which reveal the dirty details of this intense competition.

Conclusion
The Nikon 50mm f/1.8 lens has a wide aperture range (f/4-16) over which it can yield sharp (over the entire frame) photos that display essentially no distortion. Wide open, it shows considerable corner softness, but the center of the frame is only a little soft. Accordingly, it can make a good available-light lens for shooters on a bargain, at least if you can manage to keep your low-light subjects near the center of the frame. While the CA and Shading values are slightly above average in the six-lens competition, both performances are acceptable. Selling at a typical street-price of $115, it seems a particularly good buy.