Advanced Aspherical (Aa) elements, ED (Extra low dispersion) glass elements and Nano AR Coating contribute to control ghosting, flare and aberration. A 9-blade circular aperture and constant F4 aperture deliver beautiful bokeh. Advanced Aspherical optical design Four aspherical elements, including two advanced aspherical elements, effectively suppress aberrations, achieving impressively high resolution that fully satisfies expectations for the G Lens brand. Spherical aberration is a slight misalignment of the light rays projected on the image plane, which is caused by differences in refraction at different points on conventional spherical lenses which degrade image quality in large-aperture lenses. Specially shaped aspherical elements in this lens restore alignment of light rays at the image plane, maintaining high sharpness and contrast even at maximum aperture and ultra-wide angles. Well-designed aspherical elements can reduce the total number of elements required in the lens, thus reducing overall size and weight. ED (Extra low dispersion)Three ED (Extra-low Dispersion) glass elements control chromatic aberration for excellent sharpness from image center to periphery. ED glass elements correct for axial chromatic aberration and chromatic aberration, which affect resolution and bokeh, while leaving precisely rendered edges with no fringing or unnatural coloration. Nano AR Coating Sony's original Nano AR Coating technology minimizes flare and ghosting by suppressing internal reflections and maintaining clarity, even in difficult outdoor lighting conditions, for dynamic range that achieves lifelike detail and gradation with advanced camera sensors. This precisely defined regular nano-structure allows accurate light transmission, contributing to high-quality images, more so than with lenses that use coatings with an irregular nano-structure. The reflection suppression characteristic of the Nano AR Coating is superior to conventional anti-reflective coatings, providing a notable improvement in clarity, contrast, and overall image quality. 9-blade Circular Aperture When changing your aperture to defocus the background, light sources appear blurred. This 'bokeh' effect of the blurred background is enhanced with the 9-blade circular aperture used in this lens. Conventional aperture blades have flat sides creating unappealing, polygonal-shaped defocused points of light. a lenses overcome this problem through a design that keeps the aperture almost perfectly circular from its wide-open setting to when it is closed by 2 stops. Smoother, more natural defocusing can be obtained as a result. Class-leading close-up performance Class-leading close-up performance with a minimum focusing distance of 14.9 and 0.31x maximum magnification is ideal for portraits, telephoto macro, and more. Contributing refinements include ED glass elements and a floating focus