A focal length only half the diagonal of the film frame , produced with an almost symmetric lens design of surprising compactness , featuring the typical advantages of symmetrical lens designs : distortion is extremely well controlled , and so is color correction and image field flatness 只有膠片對(duì)角線長度一半的焦距、驚人的緊湊和幾乎對(duì)稱的鏡頭設(shè)計(jì),使之具有對(duì)稱結(jié)構(gòu)鏡頭的典型優(yōu)點(diǎn):控制得極好的變形、色彩矯正和像場平坦度。