SG-image AF 25mm F1.8

The SG-image AF 25mm F1.8 is a compact autofocus standard prime for APS-C mirrorless cameras. SG-image offers it for Sony E, Fujifilm X and Nikon Z, in black and silver. The 25mm focal length gives a field of view comparable to about 37.5mm on full frame, a normal view that is slightly wider than the classic 50mm equivalent. SG-image calls it possibly the slimmest autofocus 25mm F1.8 lens in the world and aims it at daily carry, travel and street photography.

Optical design

According to SG-image the lens has 7 elements in 5 groups with a 58 degree angle of view. The 9-blade diaphragm runs from F1.8 to F16, and the spec sheet lists an automatic aperture, so there is no aperture ring. The minimum focus distance is 0.3 m with a maximum magnification of 1:10. SG-image says the design uses fewer moving parts to keep distortion and chromatic aberration low, which is a manufacturer claim. No special glass types are named on the product page.

Autofocus and handling

Autofocus is driven by a motor that SG-image describes as fast, accurate and quiet, aimed at street scenes and eye focus on portraits. Aperture is controlled from the camera. The lens has a 52 mm filter thread. SG-image's product title says it comes with a metal lens hood, and the same hood is also sold separately for this lens and the AF 35mm F2.2.

Build and size

The barrel is metal. The spec sheet lists a weight of about 145 g and dimensions of 67 mm diameter and 32 mm length, while the marketing text on the same page mentions 152 g and a depth of 34 mm, so there is a small inconsistency in the manufacturer's own figures.

Where it fits

For a manual alternative from the same maker see the SG-image MF 25mm F1.8, which is slightly heavier at 186 g. In the database, the 7artisans 25mm F1.8 is a comparable manual lens, and the 7Artisans AF 24mm F1.8 is an autofocus option for full frame mounts. SG-image also sells a Micro Four Thirds version of this lens as the AF 25mm F1.8 MFT.

Pros and cons

Pros

• Very compact and light
• Autofocus with a bright F1.8 aperture
• 9-blade diaphragm
• Metal barrel
• Available in black and silver for E, X and Z

Cons

• No aperture ring
• No stabilization, which is typical at this size
• Manufacturer weight figures are inconsistent
• No weather sealing mentioned
• Limited independent test data so far

Verdict

The SG-image AF 25mm F1.8 is a small, light and inexpensive autofocus prime for APS-C cameras. It is a good fit for photographers who want a normal-view lens that disappears on the camera and do not need an aperture ring or weather sealing.