All Quark2 lenses can be refocused simply by turning the lens in its mount. No special tools are required.

Tau2 324, Tau2 336, and Tau2 640 cameras each use two types of lens mounts: one for wide field of view (WFOV) lenses; another for narrow field of view (NFOV) lenses. All lenses are set to infinity focus using a collimator at the factory. WFOV lenses can be focused using the Tau Focus Tool, part number 421-0037-00. The narrow field of view (NFOV) lenses use a locking collar secured by a 1.5mm socket head screw that prevents the lens from moving. The focus of Tau2 NFOV lenses can be adjusted by using a metric (1.5mm) Allen driver to loosen the collar.
Most legacy Photon 320 cameras use a common, threaded lens mount. The lens position is set by means of a small setscrew installed into one of two tapped holes in the side of the lens mount. To loosen or tighten this setscrew requires a 0.035` Allen driver. Care must be taken not to overtighten the setscrew, as damage to the lens threads can result. The setscrew should only be tightened with the absolute minimum force needed to prevent the lens from turning in the lens mount.

Most legacy Photon 640 cameras use a common, threaded lens mount based on a locking collar that is secured by a 1/8` socket head screw to prevent the lens from moving. The focus of legacy Photon 640 lenses can be adjusted with a 1/8` socket driver. The now obsolete 21.5mm lens version of the legacy Photon 640 was unique. This lens was integral to its lens mount, and required a special tool to re-focus.