The Sigma 12-24 f/4 Art is the latest version of the famous Sigma 12-24 lens, it is an extremely wide-angle full-frame lens. Despite the technical difficulties due to the 12mm focal length (on Full Frame) NiSi has created a 150mm filter holder that can reduce vignetting to a minimum. In 90% (or more) of the uses outdoor there is no vignetting, making the possibility of using ND filters and GND filters available to the photographer.
150mm Filter holder for Sigma 12-24mm F4 DG HSM Art
NiSi has created a 150mm holder by very precisely positioning the adapter ring and holder in such a way as to offer virtually no vignetting. Vignette only occurs when the holder is precisely 45° from horizontal. Rotating away from this “critical” decreases the vignette
Vignetting with the 150mm holder for the Sigma 12-24 f/4 ART
This simple diagram explains the vignetting of the 150mm NiSi filter holder for the Sigma 12-24 F4 Art. With small movements to the right and left there is no vignette, even at the 12mm focal length. For rotations close to 45 ° vignetting takes place as shown in the photo below, but only between 12 and 13.5mm approximately. At other focal lengths, there is no vignetting in any position.
As we can see from the image below, the maximum vignetting occurs with rotation of the holder by 45 °. In other positions, vignetting decreases or disappears completely, this occurs only at shorter focal lengths.
Thankfully, rotation at EXACTLY 45 ° is an unrealistic situation in the field. In fact, the holder is rotated only when it is necessary to align the GND filter with a particular light or feature. It is really difficult to find oneself in the situation in which it is necessary to rotate the filter holder at precisely 45°, so it is reasonable to imagine the vignetting as absent, although it is important to know that at 45 ° between 12 and 13.5mm it can occur, albeit reducing with further rotation of just 1º.