Sigma isn’t short of fast primes in its lineup, so where does this latest addition fit in? Michael Topham takes a closer look
Sigma 40mm f/1.4 DG HSM Art review: Resolution, shading and curvilinear distortion
Our Image Engineering MTF tests were carried out with the lens mounted to Canon’s 50-million-pixel DSLR, the EOS 5DS R. The solid red line spike tells us sharper results can be achieved in the centre of the frame as a result of stopping down from f/1.4, however this shouldn’t put people off making the most of the fast maximum aperture available. Corner sharpness, illustrated here by the dotted line peaks at f/5.6, beyond which point diffraction gradually takes the edge off sharpness.
Shading is noticeable in images taken at f/1.4, measuring approximately 1.5EV darker at the edge than at the centre. Stop the lens down to f/2 and this falloff is reduced to around 0.7EV, which was still visible in many of our real-world test shots. Stop the lens down to f/2.8 and vignetting can only be traced at the very far corners, disappearing completely by f/4.
The curvilinear distortion performance is just as good as Sigma claims it to be. You won’t need to fret about barrel or pincushion distortion causing problems and with a very low -0.4% distortion figure you can confidently go about your work knowing any subject with straight lines will be rendered faithfully.