What are the technological developments that have led to building and using wider and wider lenses?
I’ve been dabbling in photography for more than 50 years now. When I started, a ‘wideangle’ lens was a 35mm on the standard 35mm 24 x 36mm frame, yielding a horizontal angle of view of 54.4°. When I came to build my first system, the state of the art had advanced to allow a 28mm lens – that is, a field of view of 65.4°. By the time I got my first digital camera, 28mm was no longer considered ultra-wide. These days, a standard zoom is considered inadequate if it does not have a widest focal length of 24mm (or equivalent) with an angle of view of 73.7°. Real ‘wideangle’ is wider still. Nikon produces an f/1.8 lens with a focal length of 20mm (84.0°). Ultra-wide zooms routinely start at14-16mm (104.3° to 96.7°). Furthermore, these are high- quality lenses that, even wide open, give good sharpness from corner to corner. I have such a lens. It is not my most used lens, because it’s large and inconvenient in several ways, but the fact it exists at all is something I find quite remarkable.
I remember reading in awe an Amateur Photographer (AP) article in the 1960s about the launch of the Zeiss Hologon 15mm f/8 lens. This lens was, like my zoom, huge and unwieldy. Furthermore, its rear element was so close to the film plane that it couldn’t be used in an SLR. Zeiss sold it built into a special camera, the thought being that this lens would be in such great demand that photographers would be willing to buy an additional camera just for the privilege of owning it. Unfortunately, Zeiss was wrong, and most of the 500 lenses went unsold. Eventually, Leica bought them as a job lot and converted them to fit its M-mount rangefinders. Still, that doesn’t detract from the wonder of the lens – a rectilinear lens with a 104.4° angle of view. The AP article was very clear that this was a landmark in optical design, yet now it is commonplace. How has this come about? It’s a combination of a number of technological advances.
One is the enormous increase in availability of computing power. The Hologon was a computer- designed lens – and in fact this was part of the general air of wonder in AP’s article about it. The lens’s unique Siamesed middle element was there because that was the best configuration, according to the computer. At the time, Zeiss operated a single super-computer for optical calculations. It was a state-of-the-art and expensive machine. It had somewhat less computational power than a modern mobile phone. Consequently, Zeiss as a company was very choosy about which projects it scheduled on the machine, and how much computer time was expended. This tended to limit the design of complex lenses, or ones that would require a great many optimisation cycles. By contrast, nowadays computer power is cheap and available. A perfectly normal desktop PC can compute even a complex lens in a few hours.
The second factor is the much improved anti-reflection coatings, which allow more complex optical formulae. The Hologon was a three-element (or maybe four, depending on how you count the Siamesed inner element) design. A modern ultra-wideangle lens may have upwards of ten elements. Improved coatings allow such complex lenses without unacceptable contrast loss.
The final factor is the size of the market. Although DSLR sales worldwide are declining, they are still at a far higher level than where camera sales were 50 years ago. The larger market allows higher spend on research and development, which makes feasible what was previously infeasible.
Bob Newman is currently Professor of Computer Science at the University of Wolverhampton. He has been working with the design and development of high-technology equipment for 35 years and two of his products have won innovation awards. Bob is also a camera nut and a keen amateur photographer.