Vintage Viewfinders

Note:  Excellent optical diagrams of the viewfinders described here are available on the Early Photography site and in Camerapedia.  See reference list. Ever since the invention of the camera, designers have grappled with the problem of accurately viewing the image before the film is exposed.  Early cameras, such as the  above 1886 Instanto tailboard camera, lacked any form of independent viewfinder, employing the rear ground glass focusing screen as the only means of composing the image.  This arrangement worked in the days when cameras were large, heavy, bulky, and largely restricted to studio work. Once dry plates and roll film became available, the camera moved out of the studio, and a quicker and more convenient method of previewing the image…Continue Reading

Aperture, f-Stops, and the U.S. System

Understanding the idea of aperture, or “f-stops”, is not always a straightforward concept for beginning photographers.  There are two ways of controlling the amount of light falling on the film: the exposure time, or shutter speed, and the size of the lens opening, or aperture.  The concept of aperture is complicated by the fact that, when comparing different lenses, having the same size opening does not necessarily mean that the same amount of light falls on the film.  Rather, the amount of light admitted by a given opening depends on the focal length of the lens.  In other words, if the iris diaphragm opening is 25 mm, it will expose the film only one-sixteenth as much on a 200 mm…Continue Reading