Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens Review

The OS settings for the Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens are simply On and Off. Even when the OS switch is off, the light whirring sound indicating OS is functioning can be heard while the camera meter is active. Sigma stated to me that OS remains active to hold the lens in an optically centered position - and you see the viewfinder framing jump to a new position when the meter is activated or deactivated. Keep this in mind when framing your shot - especially when setting up a tripod-based shot (keep the meter active).

The Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens comes with a center-and-side-pinch front lens cap that is easy to get off even inside the also-included relatively small lens hood. A rear cap is always included of course.

The Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens is available in Canon (reviewed), Nikon, Sigma, Pentax (no OS) and Sony (no OS, no AF unless the body supports HSM motor) mounts. My obligatory standard disclaimer: You should know that there are potential issues with third party lenses. Since Sigma reverse engineers (vs. licenses) manufacturer AF routines, the possibility exists that a new body might not support an older third party lens. Though not common, this has happened. Sometimes a lens can be rechipped to be made compatible, sometimes not. Second, there is the risk of a problem that results in the lens and body manufacturers pointing blame at each other. However, Sigma USA's 4-year warranty is far superior to Canon's standard 1 year warranty (though many credit cards will double the Canon warranty for you).

The combination of a narrow max aperture and somewhat slower autofocusing make this lens less attractive for sports. The Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens could be a good choice for travel where it is not convenient to carry multiple lenses - or you need all these focal lengths mounted simultaneously. The price, especially for an optically stabilized lens, is good. The optical qualities leave room for improvement.

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