Studio Tests (Full frame / FX format)
The story on full frame isn't wildly different to that on DX. The 58mm F1.4 is rather soft wide open, but gets extremely sharp in the centre of the frame by F2.8. The extreme edges lag a long way behind, but in these flat chart tests, this reflects curvature of field as much as inherent (un)sharpness. In all other respects the lens does very well.
|Sharpness||Sharpness isn't all that impressive wide open, but improves very rapidly as the aperture is closed down. Central sharpness is exceptionally high at F2.8, but the corners are a long way behind. In fact they only really sharpen up properly in these tests at F8-F11. To a degree this reflects curvature of field as much as anything else - they're properly in focus at a slightly different distance compared to the centre.|
|Chromatic Aberration||Lateral chromatic aberration is very low indeed, and unlikely ever to be a problem in normal use.|
|Vignetting||Vignetting is very low. The 58mm shows just 1.3 stops falloff wide open, which equals or better any other full frame fast normal prime.|
|Distortion||The 58mm shows visible barrel distortion, and at 1.6% it's towards the high end for this type of lens. But the relatively simple profile means it should be easy to correct on the (likely rare) occasions it might be necessary.|
As you'd expect, it's a similar story on full frame to DX when shooting at the lens's minimum focus distance - just a bit more exaggerated. Wide open the image is soft across the frame, due to a combination of spherical aberration and longitudinal chromatic aberration. But while the centre sharpens up nicely by F2.8, the corners are still very soft indeed at this aperture. Indeed the lens needs stopping right down to F11-F16 for them to sharpen up fully. There's no visible chromatic aberration, but barrel distortion is quite obvious. The 58mm simply isn't all that happy when used for close-ups.
Specific image quality issues
As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests. Here the AF-S Nikkor 58mm F1.4G turns out to produce much better images than might be inferred from looking at the test results alone.
On the next page we'll directly compare aspects of the 58mm's performance to the existing AF-S Nikkor 50mm F1.4G - specifically sharpness, coma, and bokeh.
Large aperture primes can often have problems with flare when shooting into the light - all that glass means that there's plenty of opportunity for internal reflections. However the 58mm F1.4 uses Nikon's much-vaunted 'Nano Crystal Coat' to reduce flare and ghosting, so we'd hope it would perform better than usual for this kind of lens.
In practice the 58mm deals extremely well with contre-jour shooting; we've shot directly into the low winter sun and it's barely skipped a beat. It's only really discomfited with the sun right in the corner of the frame with the lens stopped down, which can result in an unsightly green flare spot in the opposite corner. But place the sun closer to the centre of the frame, and there's no problem at all. The deeply-recessed front element means that there's no problem with oblique light sources at all.
|Nikon D800, F5.6||Nikon D800, F16|
The studio tests show that the 58mm exhibits very little colour fringing from lateral chromatic aberration, and this is borne out in real world use. You have to look really, really hard at your image files to see any, and you've have to make enormous prints for it to be a problem. Nikon's DSLRs will correct it in their JPEG processing anyway.
Longitudinal chromatic aberration is visible at times, as colour fringing around out-of-focus highlights that's magenta in front of the focus plane, and green behind it. But even this isn't especially problematic most of the time. The first image below illustrates how it looks in the worst-case scenario, using 100% crops from the 36MP D800 to show CA around specular highlights. The fringing here is fairly intense in colour, but relatively narrow in width. In principle this makes it quite easy to remove using suitable tools such as Adobe's Lens Correction module. Few fast primes do better than this, and most are worse.
|Nikon D800, 1/2500sec F1.4 ISO 100||100% crops|
|Nikon D800, 1/6400sec F1.4 ISO 100||50% crop from background (lamp post)|
The second example illustrates what you'll see with a lower contrast, more distant background. If you look closely enough, green and magenta chromatic aberration is visible across a lot of the background, but because it's substantially out of focus it's not very objectionable. You'd need to print this image pretty large - probably about 24" x 16" (60 x 40cm, or A2) - for the colouration to become clearly visible.
The tests show that the 58mm F1.4 exhibits about 1.3 stops vignetting at maximum aperture, which is impressively low for this class of lens, and a consequence of its large optical unit. The fairly gentle falloff pattern also means it's not at all intrusive - in many real-world images it will disappear into the natural variations of brightness across the frame.
The example below shows the lens's maximum vignetting at F1.4 in the kind of shot where it's far and away the most visible - with an evenly-toned blue sky. We wouldn't consider this remotely problematic (in fact we'd probably say it adds to the photo, rather than detracting from it), but it's easy enough to correct in software if you don't like it.
|Nikon D800, F1.4, 1/800sec ISO 100|
One genuinely desirable, but difficult to measure aspect of a lens's performance is the ability to deliver smoothly blurred out-of-focus regions when trying to isolate a subject from the background, generally when using a long focal length and/or a large aperture. This is one area where the 58mm F1.4 shines - its rendition of out-of-focus backgrounds is almost always highly attractive, with very smooth and natural-looking tonal transitions. Occasionally a tinge of green chromatic aberration can slightly spoil the effect, but overall the 58mm works wonders at blurring away backgrounds.
We'll compare this aspect of the 58mm's imaging directly to the AF-S Nikkor 50mm f/1.4G on the next page - just for now we'll show some real-world examples.
|Nikon D7100, F1.4, close-up||Background crop|
|Nikon D7100, F1.4||Background crop|
|Nikon D800, F2||Background crop|
Sharpness and curvature of field
One quite striking characteristic of the 58mm F1.4 is that it exhibits clear curvature of field. By this we mean that the 'plane' of focus isn't flat, but curves inwards towards to the camera at the edges of the frame. A consequence of this is that if you point the 58mm at something flat - including such prosaic subjects as a brick wall or lens test chart - the corners come into focus at a slightly different point to the centre of the frame. This means that you can't both get the corners and centre of the frame at the same time, and in turn explains the striking drop-off in sharpness of the test data towards the corners - in effect they're slightly out of focus.
Alternatively, if the focus at the centre of the frame is slightly off, it's possible to get a slightly odd-looking effect where the corners of the image are visibly sharper than the centre. This is shown in the example below, which was shot on the D800 prior to setting Focus Adjust, and was distinctly back-focused in the centre. But by chance, the corners are all in much better focus. This field curvature is sufficiently pronounced to be clearly visible on the D800 at apertures as small as F4.
|Nikon D800, F4||100% crop, centre of frame (out of focus)|
|100% crop, upper left||100% crop, upper right|
|100% crop, lower left||100% crop, lower right|
A practical consequence of this is that, when shooting three-dimensional real-world images at large apertures, the corner sharpness can end up looking substantially higher than predicted by the test data, because it's entirely possible that there'll be corner detail in sharp focus. But it all depends on the subject and focus position; if the edges and corners of the frame are further from the camera than the focus point, they can end up looking softer than you might expect.