In recent years, macro lenses in the standard range have tended to employ inner focusing with the goal of maximising autofocus speed. In contrast, the new SIGMA 70mm F2.8 DG MACRO | Art lens is designed to prioritise optical performance, fulfilling the demanding image quality requirements that define the Art line. In the standard to mid-telephoto range, it delivers stunning resolution and incredible clarity that greatly exceed expectations for a macro lens. The coreless DC motor further enhances image quality, while an optimised algorithm helps offer extremely smooth autofocus performance for a weightier, high-performance lens. Photography enthusiasts will recall a certain legendary, razor-sharp macro lens – the SIGMA MACRO 70mm F2.8 EX DG – and be glad to learn it is available in a new form, updated with outstanding Art line quality.
Top-level performance at every shooting distance
In order to realise top-level performance at every shooting distance, the lens features an extending, floating, two-group focus mechanism. This configuration minimises aberration to produce optimal results at any focus distance. To minimise axial chromatic aberration, the optical system incorporates two FLD glass elements, two SLD glass elements, and one element with a high rate of anomalous partial dispersion and a high index of refraction. In addition, two aspherical lens elements help increase resolution at close shooting distances. This optical system makes possible a razor-sharp in-focus area contrasted with a bokeh area free of colour streaking.
Designed to minimise flare and ghosting
From an early stage in the lens design process, flare and ghosting have been measured to establish an optical design resistant to strong incident light sources such as backlighting. SIGMA’s Super Multi-Layer Coating produces sharp and high contrast images. The included lens hood can be attached to block out extraneous light, which can have a negative effect on rendering performance.
Exclusive low-dispersion glass
The degree to which light is refracted by glass depends on the light's wavelength. This fact causes different colours of light to focus at slightly different points. The result is chromatic aberration – the colour fringing that is particularly noticeable in telephoto lenses. Most chromatic aberration can be removed by combining a high-refractivity convex lens element with a low-refractivity concave element. Yet residual chromatic aberration known as “secondary spectrum” may still remain. To minimise this secondary spectrum, which can be a serious issue with conventional lenses, SIGMA lenses feature up to three types of exclusive low-dispersion glass offering superior performance: ELD (Extraordinary Low Dispersion), SLD (Special Low Dispersion) and FLD (“F” Low Dispersion). In particular, FLD glass offers ultra-low dispersion in combination with high transmittance and the anomalous dispersion characteristics of fluorite. Meticulous deployment of these types of exclusive low-dispersion glass and optimisation of power distribution gives SIGMA lenses superlative image rendition undiminished by residual chromatic aberration.
Focus-by-wire system for comfortable and precise focusing
The focus-by-wire system eliminates the direct mechanical connection between the focus ring and the focus drive system. Controlled by SIGMA’s latest algorithm, a newly developed coreless DC motor adjusts focus with optimal speed and low noise. Full-time manual focus is available even during autofocus, allowing the photographer to make minute focus adjustments simply by turning the focus ring. In addition, the focus ring’s large angle of rotation helps the photographer achieve the extremely precise focusing required for effective macro photography.
Fast AF with full-time manual focus
'Full-time' manual focus function allows the lens to be switched to manual focus simply by rotating the focus ring.
The 9-blade rounded diaphragm creates an attractive blur in the out-of-focus areas of the image.
High-precision, rugged brass bayonet mount
The brass mount combines high precision with rugged construction. Its treated surfaces and enhanced strength contribute to the exceptional durability of the lens.
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01 March 2018
While offering the same high-performance optical design as other lenses in the Art line, the new E-mount models will feature a newly developed control algorithm that optimizes the autofocus drive and maximizes the data transmission speed.Read full article
NB: If extremely precise autofocus is required, the Sigma calibration dock will fine-tune the relationship between the specific camera and the specific Sigma lens you are using. For ultra precision, you may also want to hire the Datacolor SpyderLENSCAL calibration chart.