Sigma 28mm f/1.4 DG HSM: Substantial Difference in White Balance / Tint for f/1.4 vs Stopped-Down (Nikon D850)
See my Sigma SLR lenses wishlist at B&H Photo.
The behavior shown here occurs in various fast lenses, not jusy Sigma lenses. It appears to be related to the Nikon D850 sensor design. See also Sigma 105mm f/1.4 DG HSM Art: Color Shift with Stopping Down, SpyderCHECKR Card.
This series uses the Datacolor SpyderCHECKER card to demonstrate that white balance (mostly tint) with the Sigma 28mm f/1.4 DG HSM Art at f/1.4 is substantially different versus stopped down.
The photographer using the Sigma 28mm f/1.4 DG HSM Art on the Nikon D850 (and presumably other cameras like the Nikon Z7) absolutely must take this large tint difference into account when processing files at f/1.4 versus stopped-down apertures.
Includes SpyderCHECKR card shots from f/1.4 through f/4 with and without neutralizing the color for the aperture, plus an outdoor scene aperture series.
Values for achieving neutrality in Adobe camera RAW are shown for f/1.4, f/2, and other apertures.