While maximizing resolution at the area in focus, this lens offers a silky-smooth bokeh affect to the front and rear. To achieve exceptionally crisp resolution, we have minimized sagittal coma flare, chromatic aberration, and every other type of optical aberration that affects image quality. The result is minute detail without bleeding or streaking, even at wide-open aperture. Moreover, we have also minimized both vignetting and color streaking to the front and rear of the area in focus, thereby establishing a bokeh effect that is natural and aesthetically pleasing.

An ideal large-aperture standard lens offers outstanding image quality across the image plane, even at wide-open aperture. Sagittal coma flare is an optical aberration in which point light sources near the image periphery have a tail (“coma”) instead of appearing round. To minimize this aberration, we have included a precision-molded aspheric lens element in the rearmost lens group. Since it minimizes the streaking of point light sources near the edge of the image, this lens is an excellent choice for shooting heavenly bodies and nighttime illumination. In addition, its beautiful bokeh effect makes it a great go-to lens for portraits, interior shots, and many other applications.

Axial chromatic aberration is difficult to correct after a photograph is taken using image processing software. For this reason, this lens features SLD (Special Low Dispersion) glass to minimize axial chromatic aberration and deliver sharp, high-contrast image quality throughout the frame.

Distortion is an optical aberration in which straight lines appear bent or curved. Since adjusting the focus cannot correct this aberration, it must be minimized at the design stage. This lens features aspheric lens elements and an optimized power distribution to minimize distortion from the center of the frame all the way to the edges.

Large-aperture lenses are prone to reduced peripheral brightness. In this lens, we have made the forward lens group large-aperture, thereby raising aperture efficiency. The result is minimal reduction of brightness at the image periphery and even image quality throughout the photograph. Even at the wide-open aperture, you can shoot a blue sky without fear of reduced brightness and achieve a beautiful bokeh effect at the same time.

The x-axis represents image height (distance from center of image in mm), and the y-axis represents the relative illumination at the edge of the image (with illumination at the center of the image defined as 100%). When relative illumination is low, the corners of the image appear dark, resulting in vignetting.

When photographing with point light sources such as electric lights or reflections on a body of water in the background, the rounded 9-blade diaphragm helps produce an attractive bokeh effect—even at large-aperture settings.

Conventionally it is considered essential to leverage the qualities of metal and polycarbonate in camera and lens layout design. A first for the industry, the barrel of the new series of SIGMA lenses features a new TSC (Thermally Stable Composite) that offers minimal thermal shrinkage combined with exceptional hardness. It also offers 25% greater elasticity than polycarbonate. Since its thermal shrinkage is low, TSC matches well with metal parts, further contributing to the high-precision construction of the lens.

The brass mount combines high precision with rugged construction. Its treated surfaces and enhanced strength contribute to the exceptional durability of the lens.