Nikon 18-55 vs 18-105

The contenders are:

• AF-S DX VR Zoom-Nikkor 18-55mm f/3.5-5.6G (not to be confused with the newer VR II version)
• AF-S DX VR Zoom-Nikkor 18-105mm f/3.5-5.6G ED

Conclusions

Which to get?

Neither lens is clearly better than the other, technically.  They have similar features and each exceeds the other in at least some areas.  But the 18-55 is slightly smaller, significantly lighter, and much more consistent in its performance.  Consequently I rate it as better value, given it’s significantly cheaper.

But, if you actually want the extra telephoto range (and the slight, undocumented wide-angle improvement) the 18-105 is a decent replacement (though in the 55-105 range you can get better quality from something like the Nikon 55-300, if you’re willing to swap lenses).  On the other hand, if you spend most of your time at the wide end of these lenses, the 18-55 is undoubtedly better.

That said, I’m only intending to keep one, and I haven’t decided which it’ll be yet.  I expected the 18-105 to be an unequivocal replacement for the 18-55, and as such I’m a bit disappointed.

Sharpness

Both lenses are pretty decent in theoretical sharpness, as tested here.  Not pixel-perfect, but high enough that a 100% crop is pretty decent.  The reality is that the differences between them are very small compared with the difference between perfectly steady “studio” shots versus real-world, hand-held use.

The difference in centre sharpness is small at all focal lengths, but the 18-55 does win almost all the time.  The differences at the edges, however, can be dramatic – with the 18-105 doing particularly poorly at shorter focal lengths.

Both lenses have surprisingly dramatic variations in sharpness across the frame in a somewhat random manner – e.g. some corners are better than others at one focal length, but their relationship can be completely different at another.  There can be significant sharpness variation back and forth multiple times across the frame, with no obvious bias like left-side-always-sharper or similar, nor any apparent relationship to actual distance from the lens.  I’m a little bit flustered by this.  I don’t know how reproducible it is or have any idea what the cause is.

Interestingly, despite it generally being a wash between the two, the 18-105 does achieve significantly higher peak, localised sharpness.  The problem is it’s not in the centre, and it’s not even a predictable spot, so I don’t know that it’s of any real use.

In terms of focal length, both are sharpest at 24mm.  45mm and 55mm are softest.

Autofocus

Neither lens displayed a bias for my particular camera (focus calibration wasn’t a deliberate aspect of my testing, but I didn’t see any evidence of consistent front or back focus with either lens, nor any favouring of one lens over the other).

Phase-detection autofocus is significantly more accurate than contrast-detection autofocus, most of the time (~70% in my limited sampling, and worse ~20% of the time).

Colour

The 18-105 had slightly better colour much of the time.  This means both stronger colours in certain hues, as well as colours that are overall closer to true life (at last according to my ColorMunki-calibrated iMac screen).

Note: I’ve found colour to be the most subjective and fungible aspect of a photo, so I don’t give this metric much weight in evaluating the lenses.  Both produce excellently-coloured images by any practical measure.

Contrast

The 18-105 had noticeably better contrast much of the time.  This was, curiously, somewhat independent of its relative sharpness.  In particular, the 18-105 did a particularly better job reproducing blacks accurately – the 18-55 never really gave a pure black anywhere in the frame (despite the smaller aperture at some focal lengths).

Chromatic aberration

The 18-55 has only slight aberration at short focal lengths, and none at all at mid-to-long ones.  It’s a very impressive lens in this regard.  The 18-105, on the other hand, has some quite significant aberration at shorter focal lengths, which only reduces to what I consider mild aberration by about 35mm.  The 18-105’s chromatic aberration is not just greater in terms of spatial shift, but also significantly more intense.

Geometric distortion

The 18-105 has more geometric distortion – especially barrel distortion at the wide end.  Both lenses have essentially no distortion at mid range, but the 18-105 picks up some slight pincushioning as it gets longer, while the 18-55 remains excellently neutral.

I did not measure the complexity of the distortion, so I can’t comment as to how easy it is to correct.  There was no waviness or non-linearity visible to the naked eye.  I use Aperture generally, so I can’t correct it anyway.  Grrr.

Aperture

The 18-105 has an on-paper ~0.3-stop advantage from 35mm on, which translates into a visible but minor improvement in illumination.  However, I also noticed that the 18-105 produces ever so slightly brighter images even at the same aperture  – on the order of about 5%, max.  The net result is that the 18-105 is ever so slightly brighter at the wide end, steadily increasing to a genuine ~0.3 stops brighter at 55mm.

Vignetting

I didn’t test for it.  Neither lens had obvious vignetting at any focal length, and if they did it’d be subjective as to whether it’s even bad to begin with, and easy enough to correct in any case.

Vibration Reduction

Not tested.  But, I did have it enabled on both lenses initially, until I realised that the 18-55 was not producing a consistent framing – it would shift significantly between viewfinder and live-view modes, and slightly between shots within the same mode, even though the camera was very firmly locked in place.  The 18-105 didn’t seem to have any such issues.  Since I, like I suspect most people, just tend to leave VR on all the time, this might be something worth considering.  The shift was significant enough that even if you’re not trying to take repeated, identically-framed shots, setting up the frame precisely for a single shot might be difficult.

Method

Note that this was done simply, quickly and not at all in a statistically reliable way (i.e. no multi-sampling, neither of lenses nor of shots).

1. Set camera (D5200) up on tripod with infrared-remote-triggered shutter, shutter delay after mirror up, and everything locked very firmly.
2. Manual mode, ISO 100, constant lighting via three CFLs.  Maximum aperture.  Focal length specified using markings on the lens barrel (or, for the extreme wide and tele ends, by rotating the zoom ring as far as possible).  Shutter speed set based on appropriate exposure at 18mm, and increased by one step for each increase in focal length (to vaguely represent necessarily higher shutter speeds, to see if the difference in maximum apertures ends up making a noticeable effect).
3. Attach first lens.
4. Focus [using phase detection in centre point] using shutter button half-press, take photo with remote.
5. Switch to live view mode, take photo with remote (which forces focusing first in centre point, using contrast detection).
6. Swap lenses.  Set new lens to same focal length.  Repeat steps 4 & 5.
7. Move to next focal length.  Move tripod so that roughly the same frame is made as at the prior focal length.
8. Goto step 4.

My test scene was a shelf of a bookcase, starting at about 50cm away at 18mm, and ending up about 2.5m away at 55mm.  The centre focus point was over the spines of two books, with sharp and contrasty writing on both.  Both books were at the same distance from the camera.  At some point I hope to compare the two with a test scene that’s at a much greater distance, to see how they perform for e.g. landscapes.

Note that I deliberately compared the lenses at wide open, which isn’t always the same aperture, because:

1. Most people shoot wide open most of the time.
2. The differences in this case were small anyway.

Detailed observations

18mm

The 18-105 in fact goes slightly wider.

They have the same maximum aperture (f/3.5).

The 18-105 has noticeably more barrel distortion – the 18-55’s is fairly subtle, whereas the 18-105’s is quite obvious.

The 18-55 is noticeably sharper for the most part, both in the centre but especially [relatively speaking] at the extremes of the frame.

The 18-105 has better contrast in places, and arguably better colour (mostly stronger).

Chromatic aberration is significantly stronger on the 18-105, both in terms of intensity and spatial shift.

24mm

They have the same maximum aperture (f/4).

The 18-55 still has very slight barrel distortion, but the 18-105 has essentially none.

Sharpness is about equal, but interestingly not consistent across the frame on either lens.  The 18-55 has a slight advantage in the very centre, but this could be luck given the wild variation across the frame.

The 18-105 generally has better contrast – but not in all places in the frame – and colour is about equivalent overall, with some parts of the frame doing better than others for one lens vs the other.

Chromatic aberration is the same as at 18mm for both lenses – i.e. the 18-55 is significantly better.

35mm

The 18-105 has a slightly larger maximum aperture (f/4.5 vs f/5 – a 0.3 stop advantage).

The 18-105 has very slight pincushion distortion, while the 18-55 has essentially no geometric distortion.

The 18-55 is sharper in the centre, but the 18-105 is slightly sharper overall.  The variation in sharpness across its frame is significantly greater than the 18-55’s.

The 18-105 has noticeably better contrast in many places.  It is as good or better throughout the frame.  It has slightly better colour.

Chromatic aberration is worse on the 18-105.  The 18-55 has no chromatic aberration anywhere in the frame.  Note however that the chromatic aberration that is present on the 18-105 is not nearly as bad as at shorter focal lengths, and is in absolute terms fairly mild.

45mm

The 18-105 has a slightly larger maximum aperture (f/4.8 vs f/5.3 – a 0.3 stop advantage).

The 18-105 has noticeable pincushion distortion, while the 18-55 has essentially no geometric distortion.

The 18-55 is slightly sharper in the centre, but the 18-105 is significantly sharper overall.

The 18-105 has better contrast in many places.  It is as good or better throughout the frame.  It has noticeably better colour.

Chromatic aberration is worse on the 18-105.  The 18-55 has no chromatic aberration anywhere in the frame.  Note however that the chromatic aberration that is present on the 18-105 is not nearly as bad as at shorter focal lengths (below 35mm), and is in absolute terms fairly mild.

55mm

The 18-105 has a slightly larger maximum aperture (f/5 vs f/5.6 – a 0.3 stop advantage).

The 18-105 has slight pincushion distortion, while the 18-55 has essentially no geometric distortion.

The 18-105 is noticeably sharper in general; very slightly sharper in the centre.  The 18-55 is more consistent across the frame.

The 18-105 has better contrast in many places.  It is as good or better throughout the frame.  It has noticeably better colour.

Chromatic aberration is worse on the 18-105.  The 18-55 has no chromatic aberration anywhere in the frame.  Note however that the chromatic aberration that is present on the 18-105 is not nearly as bad as at shorter focal lengths (below 35mm), and is in absolute terms fairly mild.