Introduction

The Sigma 135mm F1.8 DG HSM lens is a medium telephoto length lens, which is available in Canon, Nikon and Sigma mounts.

It fits into Sigma’s “Art” range of lenses, which have been designed for ultimate optical quality. It features a new large Hyper Sonic Motor (HSM), which has extra torque for quick focusing.

The design of the Sigma 135mm F1.8 DG HSM lens is dust and splash proof, meaning you can use it in a variety of different weather conditions (providing the camera you use it with is also weatherproof). It’s ideal as a full-frame lens, but you can also use it with APS-C cameras – depending on the camera you’re using, the equivalent focal length on a smaller sensor will be either 202mm or 216mm.
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https://www.photographyblog.com/reviews/sigma_135mm_f1_8_dg_hsm_review