This has been a long time in coming as I’ve been using the Nikon 20mm F1.8 G for a while. It’s undoubtedly become my favourite ultra wide angle (UWA) lens, the most used, but it’s not the best one I own.

I began my odyssey with the 20mm F1.8 G back in September, when my D810 was in for service. This means I started out using it on my Df, which has a 16mp sensor and I formed a sparkling impression of how sharp it was across the frame. I still love a lot of the shots I took with the lens early on, especially the street photography.

I revised that opinion a little when I received my D810 back as it became clearer that the 20mm F1.8 G does have a few weaknesses. These were more obvious on the 36 mp sensor. But, nothing is perfect, and I very much rate the lens.

The 20mm F1.8 G has a plastic body. Some people will hate plastic bodied lenses, but I love this lens for its small size and lighter weight (355g). It’s not as small as the 20mm F2.8 I used to own, but it doesn’t hog space like a zoom or the Sigma 50mm F1.4 ART either.

The lens has a metal mount and despite the plastic body it feels robust. For travel, this is the UWA to use. It’s also worth noting the lens has a 77mm filter thread, which allows for easy filter compatibility with other Nikon lenses.

Despite its humble construction the 20mm F1.8 G is rated as pro grade by Nikon and has their most modern nano coating as well as a relatively complex optical formula with 13 elements, of which 2 as aspherical and two are extra dispersion, all of which allows for excellent correction of optical aberrations such as Coma. You will see coma towards the edges of the frame wide open, but stopping down to F2.8 is all that’s required to remove this. All in all this is definitely a good astrophotography lens. Chromatic aberration is also well under control.

Optically, as a UWA lens it’s very predictable, but in a good way. Wide open at F1.8 you can expect a decent centre and weaker corners with lower global contrast. Once stopped down to F2.8 the lens comes into its own. The centre sharpens up significantly (I would say it’s very good at this stage) by F2.8 and the corners improve too. By About F4 the centre is at its best (I have no hesitation in calling it excellent here), but you need to go to F5.6 for the best corners. It’s worth noting that some users have reported an area of lower sharpness around the APS-C/DX corners, which I didn’t find too troubling with mine in actual landscape use, but it is there and can show up occasionally depending on the subject matter and aperture.

Stopped down the 20mm F1.8 G has nice colour rendering (it’s a Nikon, but perhaps a touch colder than the 14-24 zoom) and lovely microcontrast too. If I compare this lens with the Zeiss 21mm ZF.2, they render fine detail similarly stopped down (but the Zeiss is ahead at F2.8 and F4). The lens is clearly a modern design, but it doesn’t exhibit the kind of hyper global contrast that some modern lenses do. A bit like the Sigma 35, it is contrasty at most apertures but it strikes the right balance between global and local contrast.

There is some field curvature here, but it’s tolerable, not excessive and compares well to the somewhat excessive curvature you can get with the 14-24mm and Zeiss 21mm at most apertures. In fact the worst I can say of it is that the area of lower sharpness is a symptom of field curvature at wider apertures. I can also say this lens exhibited excellent focus accuracy all the time and I get no hint focus shift is a problem (which can be an issue for the 28mm F1.8 G).

Giving some comparisons with lenses for other brands is hard, but I’ll have a go. This lens is better than the Leica WATE, principally because the Leica is a slow, sharp stopped down retrofocus design. The Main reason to get the WATE is that it’s a good 16mm lens, not because it goes to 21mm. In contrast the Leica Super Elmar M 21mm is clearly a level above the Nikon 20. The reasons for that run through sharpness, evenness of sharpness, contrast, absence of field curvature, saturation, and size but it also costs a lot more than this Nikon lens and needs to be used on a Leica rangefinder.

Overall I rate this lens very highly. I’ve grown to like it more and more through regular use. It’s likely reaching the edge of its resolving power along the edges on a 36mp sensor, but it’s still a polished performer that’s either close to or outperforming reference lenses like the 14-24 and Zeiss 21. Comparing this to the Nikon 18-35 is also hard, both are excellent modern designs, but ultimately at its focal length (and I’ve been a sucker for a good 20/21 for a couple of years now) the 20mm is the better and faster lens than the 18-35.

To be honest I should have a UWA clear out myself and may well start warming up a well known auction website. But this isn’t a lens I’ll be selling anytime soon. It’s the always in your bag lens that actually takes amazing images (a bit like the Nikon 35 F1.8 FX). I could walk out the door everyday with this lens and a 50 and take amazing images. That’s good enough for me.

Taken with my Nikon Df, D810 and D750.

It’s worth some comment on other events too, and in the rumour mill this week is a new Canon 5D variant with a 50mp sensor. This sounds like a lot, but I imagine you’ll struggle to notice the difference from a 36mp sensor. I know I won’t be switching DSLR systems and wouldn’t buy a equivalently sensored Nikon body for a while. What will be interesting is what the 50mp sensor does to lens performance. As we know from the D800 introduction, many much vaunted lenses can fall apart in front of a higher mp sensor. However, the things I’m most interested in are high ISO and DR, in the sense of how bad is high ISO and how good is DR. I also hope Canon has paid attention to what happened to AF accuracy on the D800…