Sigma 35mm F1.4 DG HSM "Art"
Vignetting
Vignetting (darkening of the corners of the frame) should not be a big issue with this lens, as the APS-C frame only sees the "sweet spot" of the image circle. Our tests confirmed this; at F2.8 and higher, there is no visible vignetting on APS-C. There is moderate vignetting wide-open and slight vignetting at F2. All this can easily be corrected using desktop software (in-camera corrections are not available for Sigma lenses when mounted on a Pentax).