The 24mm World Cup
Qualifying Round 1: The Zooms

Leica 21-35mm f3.5-4 v Nikon 17-35mm f2.8 v Sigma 12-24mm f4.5-f5.6

Full Frame (Distortion Comparison)

Rollover each Sigma 12-24mm full frame to reveal the Nikon 17-35mm or Leica 21-35mm image.

Leica 21-35mm at 24mm (distortion)	Nikon 17-35mm at 24mm (distortion)	Sigma 12-24mm at 24mm (distortion)
1 points	1 points	2 points

The one area in which the Sigma 12-24mm scores unquestionably over the Leica and Nikon is that of geometric distortion: straight lines are captured ruler straight. The Nikon's distortion pattern is less pronounced but tougher to correct: awkward waveform/pincushion; whereas the Leica's unform barrel distortion is more noticeable, but less of a problem to fix.

For the record, in terms of distortion, the Nikon runs from barrel (17-18mm) through dead neutral (19-22mm) to various forms of pincushion (23-30mm). The Leica goes from moderately strong barrel (21-24mm) to mild barrel (25-29mm) to very slight barrel/neutral (30-35mm).

Here's what happens when you shoot walls with them: first the Sigma, then the Nikon, then the Leica:

Note also that, even when reduced to 50%, the Sigma's corners are still unsharp; the Nikon's the best.

Chromatic Aberration

The folowing crops, taken from exposures at f8, have been enlarged to 200°. At 100%, only the Leica 21-35mm demonstrated noticeable aberrations. Again, the running order is Sigma 12-24mm, Nikon 17-35mm and Leica 21-35mm:

Leica 21-35mm at 24mm (Aberrations)	Nikon 17-35mm at 24mm (Aberrations)	Sigma 12-24mm at 24mm (Aberrations)
0 points	1 points	2 points

Ouch. Conspicuously-in-need-of-attention CA problems with the Leica – quite unexpected at f8. Despite being softer than a fairy's hanky, the Sigma demonstrates truly exemplary geometric and chromatic aberration control. This 200% crop also confirms that the Nikon 17-35mm captures more information than the Leica at this aperture.