Tamron 13VM20100AS 20-100mm F1.6 Vari-Focal Lens

The Tamron 13VM20100AS is a 20-100mm F1.6 aspherical vari-focal lens designed for cameras using 1/3" image sensors — a format found in industrial imaging, machine vision systems, and compact professional video applications. The 20-100mm zoom range gives users a wide compositional spread on a single optic, covering the equivalent of a wide establishing shot through a tight telephoto on this sensor format. The F1.6 maximum aperture is notably fast for a zoom lens, enabling usable exposures in lower light conditions and providing the depth-of-field control that faster glass delivers even at the longer end of the focal range. The aspherical element design addresses spherical aberration — the optical flaw that causes blurring toward frame edges when shooting wide open — and contributes to sharpness that holds across the zoom range rather than peaking only at mid-aperture.

This is a manual iris lens, meaning aperture is set mechanically rather than electronically. That's a deliberate fit for controlled installations and studio environments where lighting is consistent and exposure is dialed in once per session. The vari-focal design — where focus shifts when the focal length changes — is standard for this lens class and requires a refocus step after each zoom adjustment. Build quality is appropriate for the specialty imaging market this lens serves, and the optical corrections are engineered specifically for the 1/3" image circle rather than adapted from a larger-format design. If your camera platform uses 1/3" sensors and your workflow benefits from a wide-to-telephoto zoom at a fast maximum aperture, the 13VM20100AS covers that range with the optical quality Tamron's aspherical designs are known for.