>The Lens Design
Design features make up the foundation of the Sigma 105mm lens. The most prominent feature is Sigma? s dedicated Optical Stabiliser system which is new to this model. The system offers an effective blur correction over 4 stops, helping to stabilize the image and counter shake. It is also linked to the viewfinder, allowing for more accurate previews and thus in focus images. The lens features Sigma? s in-house developed inner focusing system, which both eliminates the need to extend the barrel, reducing light loss, and the need to rotate the front lens. In staying fixed, the front lens can accommodate a hood (used in conjunction with the supplied hood adapter) that helps to counter light related issues such as glare. The inner focusing system also allows for the use of Circular Polarising filters. The lens also features Sigma? s exclusive Hyper Sonic Motor (HSM) which works to autofocus images in a fast, accurate and silent manner. Combined with the Optical Stabiliser system, the lens has an extraordinarily efficient focus over long distances. The lens is manufactured to Sigma? s high standards with a splash-proof body constructed from strong but lightweight polycarbonate, layered in a hard-wear paint finish.
>The Optical Composition
In all forms of lens construction, Sigma puts the highest emphasis on the quality and craftsmanship of the internal optics. As a result, the 105mm incorporates a set of cutting edge and unique optical features that work to create bright and sharp images, even at extreme close-up perspectives.
Two out of sixteen lens elements are manufactured from Special Low Dispersion (SLD) glass, renowned for its high resolution and light transmission properties. The SLD glass helps to counter various spherical and optical aberrations which are commonly found in macro lenses, such as chromatic aberration. The SLD elements also reduce field curvature and ensure high rendering performance at all shooting distances.
The lens incorporates a 9 blade diaphragm which constructs a desirable blur (bokeh) effect on out of focus areas. The diaphragm also smoothes out intense backlighting, making them appear as rounded highlights as opposed to areas of overexposure. This effect helps to overemphasize the foreground subjects and smooth out the background, creating a well-balanced image. Finally, Sigma applies Super Multi-Layer coatings to all lens elements, which work to create an optimum color balance by reducing the damaging effects of ghost and flare. The coatings also help to maximize light transmission to the DSLR? s sensor.
>A Lens Most Applicable For
With a medium focal length of 105mm and macro 1:1 magnification, this Sigma lens is a perfect match for any photographer who would like to compose close-up or portrait images. Quick and accurate auto focusing combined with a dedicated Optical Stabiliser, mean that close-up and handheld images can be composed with accuracy and ease. The greater working distance accommodated by the 105mm focal length and the silent nature of the HSM, also makes the lens ideal for taking close-up images of insects and other wildlife, subjects that by nature are easily scared off. The superior splash-proof design helps protect the lens outdoors, when in pursuit of such nature. Finally, the first-class optics allow for close-up subjects to be displayed in stunning clarity, opening up a previously unattainable world for photographers.A range of separately available Sigma APO teleconverters can be used in conjunction. The converters substantially increase the focal length of the lens and in doing so allow users to increase their working distance from a subject while still maintaining a 1:1 macro magnification.
