SG-image AF 85mm F1.8

The SG-image AF 85mm F1.8 is an autofocus portrait prime for full frame mirrorless cameras. SG-image offers it for Sony E and Nikon Z. According to the manufacturer it is compact and fast, built for portraits but versatile enough for events, landscapes and architecture. It is among the more recent additions to SG-image's autofocus range and, at 380 g, is claimed by the maker to be among the lightest autofocus 85mm F1.8 lenses.

Optical design

SG-image's own pages do not list the optical formula. Retail and database sources give 11 elements in 9 groups, including one ED element and 3 high refractive index elements. The diaphragm has 8 blades and runs from F1.8 to F16. The minimum focus distance is 0.8 m, which is also printed on the lens barrel in the manufacturer's photos, and one database lists a maximum magnification of 1:7.7. These secondary figures are not confirmed by the manufacturer's page, so they are marked as such in the data.

Autofocus and handling

SG-image describes the autofocus as reliable, quick and often silent, intended for eye focus on moving subjects. A stepping motor and internal focusing are listed by third-party databases, along with a USB-C port for firmware updates. The lens has an aperture ring marked from A (automatic) through F1.8 to F16, as seen in the manufacturer's photos, and a hood is supplied.

Build and size

SG-image states a weight of 380 g. The filter thread is 58 mm according to retailer data. Length and diameter are not published on the manufacturer's page, so they are not given here. The company describes it as significantly smaller and lighter than f/1.4 autofocus 85mm lenses, a comparison it draws itself.

Where it fits

Native alternatives in the database include the Sony FE 85mm F1.8 for Sony E and the Nikon Nikkor Z 85mm F1.8 S for Nikon Z, and the third-party AstrHori AF 85mm f/1.8 II covers Sony E, Nikon Z and Leica L. For Sony E specifically, the SG-image is a budget alternative, while the camera makers' own lenses add weather sealing and longer support.

Pros and cons

Pros

• Fast F1.8 aperture at 85mm
• Light for an 85mm full frame lens at 380 g
• Autofocus and an aperture ring
• 58 mm filter size
• Hood included

Cons

• No stabilization in the lens
• Minimum focus distance of 0.8 m is longer than some alternatives
• Optical data and dimensions come from third parties, not the manufacturer
• No weather sealing mentioned
• Only Sony E and Nikon Z versions

Verdict

The SG-image AF 85mm F1.8 offers a light, affordable autofocus portrait prime for Sony E and Nikon Z. It suits photographers who want an 85mm for portrait work on a budget and are comfortable with sparse manufacturer documentation.