4) Lens Sharpness, Contrast and Color Rendition
The performance of the 50mm is generally good, but a little disappointing when compared to the new Nikon 50mm f/1.8G lens, as revealed further down in this review. Let’s take a look at how the lens did in the lab:
The optical performance of the lens at wide apertures is not particularly impressive – you can see how weak the lens is from f/1.4 all the way to f/2.8. Once stopped down to f/4 though, the lens yields very impressive sharpness across the frame. By f/5.6, the lens reaches its maximum potential, with very good center performance and fairly good mid-frame and corner performance. The sharpness distribution is fairly even at smaller apertures, which makes this lens a good candidate for environmental portraits and landscape photography needs.
Bokeh is a very important characteristic of 50mm lenses. I would be ready to pay more for a lens that can yield better bokeh, even if it performed slightly worse than others at very large apertures.
Here is the full image from which I made the below bokeh crops:
You can see where I got the center and corner crops from. The corner crop is really not a corner, but rather an area taken from the left-center of the image. Let’s take a look at how the Nikon 50mm f/1.4G compares against the Nikon 50mm f/1.4D and Sigma f/1.4 at f/1.4 away from the center:
The older Nikon 50mm f/1.4D looks the best, followed by the Nikon 50mm f/1.4G. The Sigma definitely has the worst bokeh here; it looks as if the highlights were cut on their right side and the bokeh refractions, also known as “Onion Rings” or “Onion Bokeh” are too visible when compared to other lenses.
Now let’s take a look at the center:
Very similar results in the center as well, with the Nikon 50mm f/1.4D taking the lead in terms of “cleanness” of the background highlights. It is worth noting that the Nikon 50mm f/1.4D looks much different when stopped down beyond f/2.0 – its bokeh shape takes a form of a heptagon, due to the straight 7-blade diaphragm of the lens. Here is a more comprehensive bokeh comparison with lenses stopped down to f/2.8:
The benefits of a 9-bladed diaphragm start to become obvious when lenses are stopped down. As you can see, lenses with straight 7-blade diaphragms have a defined heptagon shape. Here is the center area crop from all lenses at f/2.8:
Which bokeh rendering do you like the most? All lenses seem to now have pronounced edges that look more or less the same. The AF-D lenses have a somewhat smooth bokeh on the inside, while refractions on both AF-S lenses are visible. When it comes to bokeh shape, I do prefer the rounded bokeh of the AF-S lenses. The heptagon-shaped bokeh on AF-D lenses looks a little distracting to the eye. But that’s me – I know some photographers actually prefer heptagon-shaped bokeh. The Sigma, again, is the worst here.
Most prime lenses heavily vignette when shot wide open and the same is true for the Nikon 50mm f/1.4G, so no surprises here. The good news is that as you stop down to f/2.0, vignetting decreases significantly. At f/2.8 vignetting is almost invisible and by f/4.0 onwards it is completely gone. Take a look at lens vignetting at different apertures shot on FX:
This type of behavior is expected from large aperture lenses, especially when they are mounted on full frame cameras. Other Nikon 50mm lenses and the Sigma 50mm f/1.4 also show heavy amounts of vignetting at maximum aperture. Enabling lens correction in Lightroom will take care of vignetting issues.
When mounted on a DX camera, the amount of vignetting is much less pronounced, with only a slight darkening of the edges at maximum aperture.
Here is how Imatest measured vignetting levels:
Here is the worst case scenario, shot at f/1.4:
7) Ghosting and Flare
Ghosting and flare are controlled well, but worse than on the new Nikon 50mm f/1.8G – see the comparison below. I performed a couple of tests with the sun in the frame and both AF-D lenses show some nasty ghosting and flares, while the newer AF-S lenses almost have none. I specifically removed the lens hoods from the AF-S lenses during this test, to show how well they perform in comparison. Part of the reason why the AF-S lenses are so much better, is because the front element on the new 50mm lenses is recessed much deeper inside the lens barrel.
If you keep the lens hood on the lens, you will get even better results when shooting against a bright source of light. Please note that the above images were taken without any filters. Using UV and other filters can potentially introduce more flares and ghosting to your images.
Unfortunately, the Nikon 50mm f/1.4G has a rather strong amount of distortion, which is very noticeable in images with straight lines. Imatest measured 1.41% barrel distortion, which is quite high for a 50mm prime (the older Nikon 50mm f/1.4D has much less distortion in comparison). The good news is that Lightroom’s Lens Corrections module or Adobe Camera RAW can take care of the distortion issue with a single click. Here is how the image looks like without any distortion corrections applied:
Note the curved lines on the top and on the bottom of the image.
Is distortion a problem? No, not at all – it can be easily fixed in post-processing software like Lightroom and Photoshop (as explained above) without losing much of the original image.
9) Chromatic Aberration
Lateral chromatic aberration is controlled well, even in high-contrast situations. The amount of longitudinal chromatic aberration (LoCA) is moderate (which is the effect of color fringing in front of and behind the focused area). Take another look at the LensAlign crop:
The above image was shot at f/1.4 and lit with 100 watt directional lamps. Stopping down the lens to f/2.8 and beyond dramatically reduces longitudinal CA.
When compared to other 50mm lenses, the Nikon 50mm f/1.4G is on par with the Nikon 50mm f/1.4D in terms of LoCA and slightly worse wide open when compared to both 50mm f/1.8 primes. Sigma is again the worst performer here.
Here is how Imatest measured chromatic aberration levels: