Laowa 105mm f/2 Smooth Trans Focus (STF)

Testers found it sharp from f/2 in the centre and excellent from f/2.8 to f/4, with the corners catching up by f/5.6. Longitudinal colour fringing is very well controlled, better than several 100mm portrait primes, and distortion is close to zero. Background blur is smooth, with milder cat-eye shapes than conventional 100mm f/2 lenses.

Veiling flare is the main weakness, and the supplied hood does little against it. Reviewers also point to rougher transitions between sharp and blurred areas, around 1.5 stops of vignetting wide open, and a noticeable colour shift between f/2 and f/2.8. Several compare it with Sony's STF lenses and conclude that the Sony blur is smoother, but at a much higher price and with slower apertures.

Owners buy it for portraits and like the creamy backgrounds, the build and the price compared with Sony's STF options. The stepless T-ring and long focus throw are popular with people who shoot video.

The common complaints are weight (745g) and length on small A7 bodies, how easily it flares against the light, and that the light loss means higher ISO than an f/2 lens would suggest. Without electronic contacts there is no EXIF or automatic focus magnification on Sony bodies.