Human vision is binocular and stereoscopic, that of the camera is monocular. This explains why so many photographs lack “depth”–the photographer, through his stereoscopic vision, saw his subject as three dimensional and forgot that, with only one “eye,” his camera “saw” his subject without depth. Unless depth is expressed in a photograph in symbolic form, the picture must appear “flat.”
The eye, guided by the brain, is selective. It sees subjectively, generally noticing only what the mind is interested in, wishes to see, or has been forced to see. In contrast, the camera “sees’ objectively, recording everything within its field of view. This is why so many photographs are cluttered with pointless subject matter. Photographers who know how to see in photographic terms edit their pictures before they take them by eliminating superfluous subject matter through an appropriate angle of view, subject-to-camera distance, choice of lens, or other means.
The eye is sensitive to color; black and white photography “sees” color as shades of gray.
However, these gray shades can be changed to a great degree through the use of color filters.
To produce pictures that are effective, a photographer who works in black and white must not only know the corresponding shades of gray for different colors, but he must also know how to change these normal shades into lighter or darker tones.
The eye does not normally notice minor changes in the color of light. Color film is very sensitive to small changes in the color of light. Since we generally do not notice small changes in the color of light which, however, cause corresponding changes in the color of objects, we are astonished when we see such changes recorded on color film. It is the failure to notice such changes in the color of the incident light which accounts for the majority of color transparencies in which color appears “unnatural.” However, if we could compare such transparencies with the subject seen under the same conditions under which the picture was made, we would most likely find that the color film was right and your judgment wrong. Later I’ll have more to say about this phenomenon color adaptation which is the most common cause of apparently “unnatural” color transparencies.
The eye cannot store and add up light impressions—the dimmer the light, the less we see, no matter how long and hard we stare. Photographic emulsions, however, can do this and, within certain limits, produce images whose strength and clarity increase with increases in the duration of the exposure. This capacity to accumulate light impressions makes it possible to take detailed photographs under light conditions of a level so low that little or nothing can be seen by the eye.
The eye is sensitive only to that part of the electromagnetic spectrum which we know as light.
Photographic emulsions, sensitive also to other types of radiation, such as infrared, ultraviolet, and X-rays, make it possible to produce pictures which show familiar objects and new and more informative forms as well as to show many things otherwise invisible.
The focal length of the lens of the eye is fixed, but a camera can be equipped with lenses of almost any focal length. As a result, the scale of the photographic image is virtually unlimited.
The angle of view of the eye is fixed, but lenses range in angle of view from very narrow to 180 degrees. Unlike our own vision, a photographic angle of view can be chosen to give a desired effect.
Our vision functions so that we see three-dimensional things in the form of rectilinear perspective. Although most photographic lenses are designed to produce this type of perspective, other lenses produce perspective that is cylindrical or spherical. The remarkable properties of these types of perspective make it possible to create impressions and show relationships between a subject and its surroundings which are beyond the scope of other graphic means.
The focusing range of the eye is severely restricted in regard to near distances; anything closer than approximately 10 inches can be seen only indistinctly, increasingly so, the shorter the distance between the subject and the eye. And small objects can be perceived less and less clearly the smaller they are, until a limit is reached beyond which they become invisible to the naked eye. The camera, however, equipped with a lens of suitable focal length or in conjunction with a micro scope, has none of these restrictions.
To the normal eye, all things appear sharp at the same time (this is actually an illusion caused by the ability of the eye to constantly adjust focus as it scans a scene in depth). The camera produces not only pictures in any desired degree of unsharpness, but can also make pictures in which a predetermined zone in depth is rendered sharp while everything else is unsharp. The eye adjusts almost instantly to changes in brightness, its pupil contracting and expanding as it scans the light and dark parts of a scene. The “pupil” of the camera, the diaphragm, can be adjusted only for overall brightness.
The contrast range of our vision is thus much wider that that of a photograph (exception: photographs taken on XR film which has a contrast range of 100,000,000:1); we can see detail in the brightest and darkest parts of a scene whereas in a corresponding photograph, if contrast was high enough, such areas would be shown as overexposed, detailess white, and underexposed, detailess black.
To compensate for the limited contrast range, a photographer must check the brightness range of his subject with an exposure meter (since his eye is untrustworthy in this respect) and if contrast is excessive, he must take appropriate counteraction.
The eye cannot function virtually instantaneously, cannot retain an image, and cannot combine a number of successive images in one impression. The camera can do all three. As a result, a photographer cannot only superimpose different images in one picture, but also express movement graphically, either by instantaneously “freezing” the image of the moving subject or by symbolizing motion through blur and multiple images and thus expressing movement in heretofore unknown beauty and fluidity of form.
The eye notices and accepts as normal the apparent converging of receding parallel lines in the horizontal plane. However, as a rule, it does not notice in reality, and rejects as “unnatural” in picture form, the apparent convergence of receding parallel lines in the vertical plane. The camera does not make a distinction between horizontal and vertical parallels but treats them alike. The result is well known in photographs of buildings and is generally considered a fault.