APO-SUMMICRON-SL 90 f/2 ASPH.

All glass elements in an optical imaging system – for example lenses – refract light in certain colours to a different extent. This leads to the effect that not all rays of light from a multi-coloured subject are focused at a single imaging point – the result of this is chromatic aberration. In order to reduce this chromatic aberration to a hardly perceptible minimum, both new Summicron-SL lenses are apochromatic – in short: APO – corrected. For this, most of the eleven elements of the optical system – one of which is an aspherical – feature anomalous partial dispersion and are manufactured from sensitive and specially formulated, high-quality glass types.

Both the construction and the design of the cutting-edge Summicron-SL line represent the next step forward in the development of lenses for the Leica SL-System. New, extremely precise manufacturing methods and measuring technologies have been developed especially for the production of these lenses. The results of this are reflected not only in the more compact dimensions and considerably lower weight of the lenses, but also in their excellent imaging performance. In addition, these lenses feature a new, faster autofocus system and a considerably shorter close focusing limit.

As both Summicron-SL primes deliver extremely high imaging performance at their largest aperture, the lenses are also ideal for photography in difficult lighting conditions. The Leica promise of ‘maximum aperture is a usable aperture’ also applies to the new SL-Lenses – stopping down is exclusively a creative imaging tool, and is not necessary for achieving better imaging performance.

In the construction of the APO-Summicron-SL lenses, particular attention has been paid to the prevention of stray light and reflections. Together with an optimisation of the optical and mechanical design, the application of high-quality coating to lens surfaces reduces unavoidable reflections to an absolute minimum.

The autofocus drive of all SL-Summicron lenses employs extremely powerful and robust stepping motors with DSD^® (Dual Syncro Drive™). Thanks to these, the entire focusing throw can be travelled completely in only around 250 milliseconds.