DISTORTION
Here’s how distortion compares for all of the lenses on test
You can expect some barrel distortion with ultra-wideangle lenses, but it tends to become less with zoom lenses as you extend through the zoom range. For direct comparison, this chart shows the relative amounts of distortion for prime lenses and zooms at their shortest focal length. The APS-C format Canon EF-S 10-18mm does well to minimise distortion, as do the full-frame Canon RF 15-30mm and Sigma 14mm prime. By contrast, the Canon RF 14-35mm and RF 16mm rely heavily on automatic in-camera correction, but that’s become more common with recent lenses for mirrorless cameras.