Sharpens edges by reducing ‘colour fringing’
Chromatic aberration occurs when a lens element refracts different wavelengths of a ray of light – its rainbow colours – at very slightly different angles. This results in the ‘colour fringing’ that reduces the sharpness of an image. LD elements are made from special glass materials with extremely low dispersion indices (i.e. the refraction of a ray of light into rainbow colours is extremely narrow). Thus they effectively compensate for chromatic aberration at the centre of the field (on axis), a particular problem at long focal lengths (the telephoto end of the zoom range), and for lateral chromatic aberration (toward the edges of the field) that often occurs at short (wideangle) focal lengths.
Although costly, LD glass materials result in clear, vivid image quality.
Extra Low Dispersion
Dispersive properties even lower than LD elements
Extra Low Dispersion lens elements are made from a special high-grade glass that has dispersive properties (i.e. where refraction causes the dispersion of white light into spectral hues) even lower than standard LD lenses, in fact being similar to those of fluorite. In combination with LD elements, these make for an optimal optical design that delivers superb resolution with advanced correction of axial chromatic and magnification aberrations – major inhibitors of image quality.
The result is a lens that delivers sharp contrast and better descriptive performance throughout the entire zoom range.
Attention-grabbing blur effects at wider apertures
Use depth of field more creatively with spectacular but natural-looking background blur.
The rounded outline diaphragm of the lens is retained even when stopped down to f/5.6. Blur highlights in a photo reflect the shape of the aperture, and they are a much more prominent feature at wider apertures. Especially in higher-speed lens, this important optical design element results in more attractive, natural-looking images.