The Sigma 18-125mm f/3.8-5.6 DC OS HSM Lens offers a high zoom ratio lens solution to digital SLR cameras, allowing you to zoom from wide-angle to long telephoto.This lens has now been updated with the OS (Optical Stabilizer) system, which minimizes image blur caused by camera shake, and offers the equivalent of shooting at a shutter speed 3-4 stops faster. This allows handheld telephoto zoom shooting even in poorly lit conditions.
The 18-125mm's optical design incorporates aspherical lenses and SLD (Special Low Dispersion) glass, which provides the utmost correction for all types of aberrations. It also enables this high zoom ratio lens to be housed in a compact and lightweight construction.
DC lenses are exclusively designed for digital SLR cameras. The image circle (rear of lens) is sized to match the smaller dimensions used for the image sensor on digital cameras. As a result these lenses are also more compact and lightweight, and are better matched to digital SLR cameras.
The OS system uses two sensors inside the lens to detect vertical and horizontal movement of the camera. It works by moving an optical image stabilizing lens group, to effectively compensate for camera shake. It automatically detects movement of the camera and compensates for camera shake when shooting moving subject such as motor sports.
Special Low Dispersion (SLD) glass, a molded glass aspherical element and two hybrid aspherical elements provide excellent correction for all types of aberrations.
Super Multi Layer (SML) coating reduces ghost and flare.
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.