Zoom Lens (1901) | Allen brings a sharper focus to photography

 Although the first zoom lens was invented in 1901 by Clile C. Allen, its popularity in sales terms only came in the late 1980s. Prior to this the fixed-focus lens was the standard; however, this was pushed aside because of the physical effort required to photograph different sized subjects. With a fixed-focus lens, the only way to adjust the amount captured in a photograph is to physically move backward or forward with the camera. 

A zoom lens works by allowing the photographer to widen or shorten the focal length, which increases or decreases the magnification of the subject. The focal length is the distance between the lens and the point in the camera at which the light rays converge. Changing this length allows you to zoom in and out when taking a photograph. 

Allen's patent application for an "optical objective" approved April 1, 1902

There are many different designs of zoom lens. Some may be composed of up to thirty individual lenses feature a final focusing lens among other moving parts. However, all of these lenses feature a final focusing lens that ensures the image remains crisp and sharp as the focal length changes. This was a major improvement on the nineteenth-century varifocal lenses, which did not remain focused after changes to the focal length and had to be refocused each time. Allen's zoom lens was therefore instrumental in making photography both more efficiently and relatively effortless. 

Early zoom lenses tended to produce lower quality images, compared with those obtained using a fixed-focus lens. However, with the advent of digital photography and computer optimization, modern zoom lens cameras have quickly caught up with their fixed-focus lens counter parts.