Purely considering ‘accutance, resolution, and microcontrast – ability to deliver maximum reality to the sensor – we can summarise thus:

• At 17mm, the lenses are equally sharp.
• At 21mm, the lenses are very, very similar – but the Nikon is slightly better.
• At 24mm, the Nikon is undeniably better.
• At 35mm, the Nikon is slightly better.

The Nikon’s advantage lies mainly in its excelling f8-f11 performance. Your particular  shooting priorities will determine how important that is. If you work mainly at f11, that factor alone might bias you in favour of the Nikon.

However, considering flare resistance and correction for distortion and chromatic aberration, the Contax holds all the aces. It handles bright lights with uncommon aplomb and has exemplary correction for colour fringing.

Not to be underestimated is the sheer practicality of having such high quality optics mated with the convenience of autofocus and auto-aperture. Occasionally, you will get shots with the Contax that you would miss while faffing about with the Nikon’s manual controls on a Canon body.

In terms of build quality, reliability and handling, they are both indisputably from the top drawer. The Contax is a lot more expensive, but it could hardly be considered overpriced when you consider the package you get. And the Conurus conversion is irreproachable.

Whether the Contax is the lens for you will depend much on your preferred working methods, post-production skills and priorities: are you intending to use the lens primarily at 17-24mm or the 24-35mm? If the latter, you’d be better off hunting down a good copy of a Canon 16-35L or Leica 21-35mm.

If you’re looking for the best thing in the 19-23mm range, there is no substitute for the Distagon 21mm at the time of writing. If you’re wondering whether the Contax N 17-35mm is the next best thing, it may well be: but if you can live without the automation, and are prepared to build a few extra Photoshop actions into your workflow, the Nikon 17-35mm f2.8 will deliver equally stunning images for a lot less money – as long as you’re careful to avoid flare.

If the Contax didn’t suffer from a torus of low resolution around the centre frame, particularly at distance, it would be so much better than the Nikon you could cry. In response to questions about the size of ‘Area B’, I’ve added blue and red overlays to the Contax 17mm shot to show where it underperforms and outperforms the Nikon which, (coincidentally) has exactly the opposite problem. Here, blue is good (for the Contax) and red is bad. As you’ll notice, the worst of it is all at middle distance: at short range the problem was less evident in the test shots.

Contax N 17-35mm: Resolution Dip

The final score, via our most recent, pretty arbitrary, grading system that simply puts a notch on the belt of the lens that performs best in each subcategory (ie, 24mm / f5.6: corners), proved to be 33 points for the Contax and 53 points for the Nikon.