Sigma has adapted its outstanding Sigma DG HSM Art lens line to Sony mirrorless by extending the rear of the lens barrel. Since it was designed for a DSLR, the optical design is ray angle friendly for digital sensors.
This scene is an excellent illustration of how a less than optimal choice of focus along with some field curvature can conspire to hamper the depth of field zone versus the subject matter.
Sigma FE 14mm f/1.8 DG HSM Art Aperture Series: Tenaya Canyon Pool
Images at sizes up to full camera resolution.
Tenaya Canyon Pool
f9 @ 1/50 sec, ISO 100; 2018-09-08 17:09:40[low-res image for bot]
Sony A7R III + Sigma 14mm f/1.8 DG HSM Art
ENV: Tenaya Canyon, altitude 8000 ft / 2438 m
RAW: LACA corrected, diffraction mitigating sharpening