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Product Description

Fig. 17-70 mm F2.8-4.0 DC macro HSM detailed image from 17-70 mm F2.8-4.0 DC macro HSM.

Enlarge Sigma 17-70 mm F2.8-4.0 DC Macro HSM.

The most important features of a standard zoom lens for digital SLR cameras are: ensuring high image quality, meeting the needs of a wide range of occasions, and being handy and compact. The 17-70mm F2.8-4 DC MACRO HSM eliminates the usual limitations of a standard zoom and offers a short close-up focusing distance, sufficient focal distance and a comfortable light intensity. The lens mainly used for everyday photography situations offers a focal length range equivalent to 25.5-105mm, based on a 35mm camera. Equipped with an initial light intensity of F2.8, the zoom is surprisingly compact. It is not only suitable for the popular travel or family snapshots, but also for slightly more creative photos. This lightweight lens is easy to carry with you and is easy to use and will satisfy even the most demanding photographers thanks to its ease of use.

The small size makes a big difference for an everyday lens. By installing a smaller OS unit and optimizing the structure and power distribution of the optical components, the lens housing became even more compact. To ensure high precision, the new composite material TSC (Thermally Stable Composite), which has a high metal affinity, is used in the lens housing. This leads to better parts durability and smaller zoom and scale rings. The dimensions of this lens are 30% smaller than our conventional models. This lens includes 2 FLD ("F" low dispersion) glass elements whose imaging performance is equivalent to that of fluoride glass, 1 SLD (specially low dispersion) glass element and 3 aspherical glass lenses, including a double-sided aspherical lens. By optimising the performance orientation of the lens, both the lateral color errors and longitudinal color errors have been corrected. It achieves excellent image quality over the entire zoom range, from infinity to macro. The Sigma Super Multi Layer coating reduces stray light and ghosting and delivers sharp and high-contrast images even in backlight. The HSM (Hyper Sonic Motor) drive ensures the fast and silent AF that can be manually intervened at any time. With the improved AF algorithm, a smoother AF is achieved.

The Contemporary product line combines high optical quality with compact design and is suitable for a wide range of applications. By incorporating the latest technology into these lenses, Sigma has solved the difficult problem of reducing size and weight without compromising optical quality.

In addition to sports photography, the lenses are also ideal for nature shots of birds, wildlife and others from the animal and plant world, as well as photos of planes, trains, racing cars and more. Another essential feature of our Sports product line lenses is the customer-specific adaptability for a wide range of functions: thanks to the software provided, all types of settings can be adapted to the photographers personal preferences.

First of all, the coating technology and the construction of the DC lenses, whose calculations are based on digital demands, largely prevent light reflections from the sensor on the backward objective lens. In addition, the DC lenses offer impressive image quality despite their low weight and compact size, which meets the demands of digital SLR cameras. These lenses are limited to the angle of view that is only used by most DSLR cameras anyway – to the angle of view of the cameras with a sensor size in the so-called APS-C format. The sensors of most digital SLR cameras are smaller than the 35mm film with its 24x36mm format and have the dimensions of the APS-C film format. Therefore, you cannot use the DC lenses on a full-frame digital camera or an analogue film camera. They inevitably received shadows in the corners of the picture. By limiting the image angle to this APS-C format, it is possible to achieve a considerable image performance with reasonable design effort. The less complex design affects the size and weight of the DC lenses. The lower effort ensures significant cost savings, which we pass on to our customers. With our DCs you get powerful lenses at extremely attractive prices.

When DC series lenses are used on 35mm SLR cameras or digital cameras whose image sensors are larger than APS-C format, vignetting occurs in the image.

HSM lenses use a motor driven by ultrasonic waves. This technology gives you a very fast, accurate and almost silent mode of automatic focus. Two different types of HSM ultrasonic drive are used in our lenses. On the one hand, the HSM ring motor, which is mainly installed in the high-quality EX lenses. This HSM drive allows you to manually intervene in the AF operation at any time. On the other hand, an HSM micromotor is mainly used in compact lenses, the so-called all-round zoom lenses. Manual intervention in AF operation is not possible.

MTF measuring system "A1".

The MTF (modulation transfer function) is one of the measuring methods with which the performance of a lens and its contrast behavior can be determined at different spatial frequencies. The horizontal axis expresses in millimetres the distance of the centre of the image to the edge of the picture, the vertical axis expresses the contrast value (highest value is 1).

The information for 10 lines/mm reflects the contrast behavior of the lens (red lines), the values for 30 lines/mm express the resolution (green lines), each with the aperture open. Lines that run parallel to the image circle diameter are called sagittal lines (solid line), transverse lines are called tangential lines (dashed line).

Previously, we measured the performance of our lenses with MTF measurement systems that used conventional sensors. Meanwhile, however, we have developed our own MTF (Modulation Transfer Function) measuring system "A1", which uses the 46 megapixel Foveon direct image sensor. Even previously undetectable high-frequency details have now become verifiable as part of our quality control.

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