The Magic of the Lens

Do you ever stop to think about your lenses, besides wanting a shiny new one? There is a magic of the lens that we seldom consider and perhaps do not even understand.

Many constraints
My perception is colored by my background as an engineer. I see a modern lens as serving so many constraints that it is a wonder they do the job as well as they do. We expect high resolving power and “good” bokah. It needs to have a good zoom range but be small. It must be weather sealed and rugged, but inexpensive. And, of course, issues like low chromatic aberration and great edge to edge sharpness and low distortion and minimal light falloff (vignetting) and minimum flare are all givens. Oh and blazing fast auto focus, too.
The poor lens designers are in a tight place. Luckily for them computer design tools have advanced greatly. Also, new materials are available to help overcome some of the design problems of the past.
Still though, we ask a lot of a professional grade lens. Probably more than we rea...