A short history of camera lenses

Simple lenses and the achromat

The earliest photographic lenses were a single curved piece of glass, often a meniscus shape that William Hyde Wollaston adapted for the camera obscura in 1812. Stopped down to around f/14 or smaller, it gave acceptable sharpness in the centre but little light.

A single lens bends colours by different amounts, so blue and red focus at slightly different distances. Charles Chevalier in Paris joined two glasses of different types into an achromatic doublet, cancelling most of that colour error. A Chevalier lens of this kind was fitted to the early daguerreotype cameras of 1839.

These lenses were slow. With daguerreotype plates, exposures could take many minutes, too long for comfortable portraits.

The Petzval portrait lens

In 1840 the mathematician Joseph Petzval in Vienna calculated a lens with about f/3.6, roughly 16 times brighter than the slow landscape lenses of the day (approximate). Voigtländer manufactured it.

It was sharp in the centre and softer towards the edges, with a swirling background blur that some photographers still seek today. For portrait studios it cut exposures to well under a minute.

Petzval's design was one of the first lenses worked out by careful calculation rather than trial and error.

The Cooke triplet and the Tessar

In 1893 Harold Dennis Taylor of T. Cooke & Sons in York designed a lens of just three elements: two positive lenses with a negative one between them. The Cooke triplet controlled most aberrations with remarkably few parts and became a model for designers.

In 1902 Paul Rudolph at Carl Zeiss introduced the Tessar, with four elements in three groups. Zeiss marketed it as the “eagle eye” for its sharpness, and versions of it were used in cameras for most of the 20th century.

Larger designs such as the double-Gauss type, the basis of most standard 50 mm lenses, came out of the same tradition.

Coatings: beating reflections

Every glass surface reflects some light, roughly 4 to 5 percent for uncoated glass. In a lens with many surfaces this causes flare and low contrast, which limited how many elements designers could use.

In 1935 Alexander Smakula at Zeiss developed a thin anti-reflection coating. It was kept for military use at first and reached the wider market around 1939.

Multi-layer coatings followed in the 1960s and 1970s. They made complex lenses with 15 or more elements practical, including the zooms we use today.

Zooms and aspherical elements

Early zoom lenses were built for film and television cameras. The Voigtländer-Zoomar 36–82 mm of 1959 is usually named as the first zoom for 35 mm still cameras. Early zooms were bulky and less sharp than fixed lenses; better design and coatings closed most of that gap.

Aspherical elements have surfaces that are not part of a sphere. They correct aberrations that would otherwise need several extra elements, but they were hard to grind. Moulded glass and plastic aspheres made them common from the 1980s onwards, and they are now in almost every lens and phone camera.

Autofocus and stabilisation

Autofocus reached consumer cameras in the late 1970s with compact cameras such as the Konica C35 AF (1977). The Minolta Maxxum 7000 of 1985 (also sold as the 7000 AF and α-7000) made it standard on SLRs.

Optical image stabilisation moves a lens group to counter hand shake. Nikon first used it in a compact camera in 1994, and Canon released the EF 75–300 mm IS lens in 1995. Later cameras added sensor-shift stabilisation inside the body.

Both features changed how lenses are built: lighter focusing groups for faster motors and floating stabiliser groups inside the barrel.

Mirrorless lenses and phone modules

Without a mirror box, mirrorless cameras let the rear of the lens sit much closer to the sensor. Designers use this shorter distance for sharper wide-angle lenses and very bright apertures. Panasonic's Lumix G1 of 2008 is usually named as the first mirrorless interchangeable-lens camera.

Phones cannot fit a zoom lens, so they carry several fixed lenses side by side, typically ultra-wide, wide and telephoto, and switch between them. Some use a folded “periscope” design that turns the light 90 degrees to fit a longer focal length in a thin body.

Software then merges, sharpens and corrects these tiny lenses. Distortion and colour fringing that once needed extra glass are now often removed after capture.