Two ED (Extra-low Dispersion) elements and PGM aspherical lenses control chromatic aberrations while enhancing sharpness and contrast. Exclusive Nano Crystal Coat further reduces ghosting and flare for even greater image clarity. Internal Focus (IF) provides fast and quiet auto focusing without changing the length of the lens, retaining subject-working distance through the focus range. Rugged construction and professional-grade dust and moisture resistance. M/A Focus Mode switch enables quick response to changing situations between Auto and Manual focus operation.