Essai du Sigma 56 mm f/1,4 DC DN | Contemporary sur Sony Alpha 7R II en mode APS-C par Arkadiusz Olech et Maciej Latałło pour LensTip.com :Sigma C 56 mm f/1.4 DC DN review - LensTip.com
Points forts :
- fût de bonne qualité
- qualité d'image sensationnelle au centre
- résolution décente sur les bords
- faible aberration chromatique longitudinale
- aberration chromatique latérale légère
- pas de problème d'aberration sphérique
- astigmatisme modéré
- bon rapport qualité / prix.
- performance atypique sur les bords
- forte distorsion
- énorme vignetage.
Two Sigma models I’ve tested lately, the A 40 mm f/1.4 DG HSM and the smaller C 56 mm f/1.4 DC DN, can be positioned on two polar opposites. The first one is a physically huge instrument, constructed without any compromises, with fantastic optics but also a high price tag. The second one is a lightweight, handy optical device, aimed at amateur photographers; its price reflects well their average budget. Small wonder such a lens features many compromises. I could accept the weaker distortion and vignetting performance without a murmur because a fast lens in a small casing has to have a significant brightness loss. Also I am able to understand lack of optics distortion correction in this class of focal lengths; after all camera software can correct that aberration easily and, with such an angle of view, cropped images are hardly an issue.
Still weak image quality on the edge is a drag. There is a big discrepancy between resolution results in the centre and on the edge: while in the frame centre you see resolution records putting to shame the performance of lenses produced by the biggest players of photographic market, on the edge you experience a slump as the lens never reaches 60 lpmm. Perhaps it is not a significant problem for an instrument which is going to be used to take portraits or a shallow depth of field shots; still there are uses where even performance across the frame is more than advisable, even for such a focal range as this one.
All the remarks, presented above, don’t change my very positive assessment of the tested Sigma. It is another excellent optical instrument, offered at a sensible price; it shows that pricing of other producers of mirrorless devices is really over the top.