The Sigma 18-250mm F3.5-6.3 DC OS HSM Autofocus Zoom Lens utilizes an anti-shake compensation function, with a 13.8 times zoom ratio. This lens's Hybrid Optical Stabilizer provides not only an anti-shake function for the camera body, but also compensates for image shaking in the view finder as the Optical Stabilizer is built in to the lens.
Four special low dispersion glass elements and three aspherical lens elements, results in excellent image quality throughout the entire zoom range. With a minimum focusing distance of 17.7" at all focal lengths and a maximum magnification of 1:3.4 reproduction ratio, this wide-range zoom is great for close-up photography as well as for telephoto shooting.
This is the magnifying factor of a lens. Macro lenses will often be described by their “magnification factor”. A lens with a 1:1 magnification factor produces a projected image on the sensor which is the same as the subject.
The individual pieces of glass that form the overall optical construction. Most lenses have between four and eleven elements to bend the light rays to ensure a perfectly formed image appears on the light sensitive surface, such as a film or CCD. The elements are arranged in groups and may be seen in specification sheets as, for example, 6 elements in 4 groups. That configuration may have two single elements and the other four grouped in pairs.
A lens with a 1:1 magnification factor produces a projected image on the sensor which is the same as the subject. A 1:1 magnification factor is usually considered the minimum for a lens to be described as a “macro” lens. Specialist macro lenses are often 1:3 or even 1:10 magnification factors, meaning that 1mm across the subject becomes 3mm or 10mm when projected onto the sensor, thus 3 or 10 times magnification.