Source: {"pile_set_name": "USPTO Backgrounds"}

Photographic cameras have been in widespread use for quite some time. Basically, such a camera operates by exposing a portion of a light sensitive media, i.e. a frame of film, for a pre-defined period of time to scene illumination. The light is focused on the frame through a lens that has an aperture of a given, often variable, size. A shutter, situated behind the lens and in front of the film, opens for a selected period of time in order to permit the light to transit therethrough, illuminate and expose the film. As a result of being properly exposed and subsequently developed, the film undergoes a photochemical process, on a two-dimensional basis throughout the frame, that locally varies the optical transmissivity of each portion of the frame in proportion to the amount of illumination that reaches that portion of the frame from a corresponding portion of the scene, thereby producing, depending upon whether reversal or negative film is used, either a two-dimensional positive or negative optical image of the scene. As such, tonal variations that appeared in the scene are captured in the frame of the film. Photographic prints are often made from negatives, while
transparencies (commonly referred to as "slides") are made from positives.
Though this overall process, which relies on the use of silver halide as a photosensitive reagent in film, has basically remained unchanged over many years, this process is highly non-linear and subject to a great many variables which significantly complicate its use. In particular, exposure (E) is defined, under a standardized definition, as being a product of the illuminance (I) multiplied by the time (t) during which the film is exposed to this illumination. In this regard, see specifically ANSI (American National Standards Institute) standard PH 3.49-1971 "American National Standard for General Purpose Photographic Exposure Meters" (re-affirmed in its entirety with no modifications in 1987 as ANSI standard PH 3.49-1987) [hereinafter referred to as ANSI standard 3.49-1987], and also ANSI standard PH 2.7-1986 "American National Standard for Photography--Photographic Exposure Guide" and specifically page 13 thereof. In a camera, the combination of two settings, namely lens aperture (size of the lens opening) and shutter speed (time during which the shutter remains open), primarily defines a particular exposure. Unfortunately, lens aperture and shutter speed define more than just an amount of exposure, these settings also dramatically affect picture (hereinafter including both prints and transparencies) quality and must be judiciously chosen in each photographic situation; otherwise, a picture (also referred to hereinafter as an image) having inferior quality will result.
To illustrate the variability among photographic parameters and the difficulties in choosing appropriate lens aperture and shutter speed settings, consider for the moment a particular scenario that often occurs and presents significant challenges to a photographer: photographing a scene in relatively low light conditions with sufficient depth-of-field to cover a desired subject. In dealing with a low light situation, a photographer, particularly an amateur, might, at first, open the lens aperture to its maximum value in order to pass as much light as possible therethrough to the film. A suitable shutter speed would then be chosen based on scene luminance, typically using an indication provided by an internal light meter located in the camera. Unfortunately, such an approach might fail. Specifically, while, the lens aperture size specifies the amount of light that instantaneously strikes the film, this size also defines the so-called depth-of-field in the resulting photographed image, i.e. a range of minimum to maximum camera-to-subject distances in which objects located therein will be perceived in the image as being sharp and in-focus. As the aperture size of a given lens increases, i.e. the lens is opened and its so-called "f" number decreases, which ordinarily occurs in low light conditions, the depth-of-field produced by that lens correspondingly decreases. Accordingly, with certain subject thicknesses, the depth-of-field that results from a maximum lens aperture exposure may be too restricted to fully cover the entire subject. Thus, portions of the subject located at camera-to-subject distances that are outside the range specified by the depth-of-field for the given lens aperture, i.e. too close to or too far from the camera, will appear out-of-focus in the resulting photographed image. Therefore, in order to provide an appropriate depth-of-field to cover the entire subject, a smaller lens aperture than the maximum available size must be used along with a slower shutter speed to generate a sufficient exposure. Unfortunately, a photographer is often unable to steadily hold a hand-held camera for times typically in excess of, for example, 1/50th of a second for a 50 mm lens. Hence, as the shutter remains open for increasingly longer periods of time, the camera becomes increasingly sensitive to camera shake or subject motion which, when it occurs, blurs and ruins the entire picture. Therefore, to reduce the incidence of noticeable image blur, particularly resulting from camera shake, shutter speeds equal to or slower than of 1/50th second for use with a 50 mm lens should be avoided for use in a hand-held camera. Consequently, other techniques, such as mounting the camera on a tripod or using an auxiliary light source, e.g. a so-called flash unit, or higher speed film, i.e. a more sensitive film, are often required in order to provide acceptable combinations of lens aperture openings and shutter speeds in low light conditions. Unfortunately, a flash unit or a tripod may not be currently available. Also, films that are increasingly sensitive tend to produce pictures that exhibit increasing graininess, thereby adversely impacting the quality of the picture. With this scenario and in the absence of having a flash unit, a tripod or the ability to change film for use in photographing a particular low light scene, the photographer may not be able to select shutter speeds and lens aperture sizes that will produce a picture of optimum quality. Instead, the photographer is forced to accept compromise settings which will likely produce a picture of sub-optimum quality, such as being under-exposed, but, owing to the latitude in the performance of the film, will hopefully still exhibit sufficient quality to still be acceptable to a viewer. To a certain extent, the developing process can compensate (through so-called "forcing") for under-exposure conditions, though the ability to do so and still provide pictures of sufficient quality depends upon the subject matter in the scene and hence can be rather limited. In this regard, see D. M. Zwick, "The Technical Basis of Photographic Speed Determination or What is a Normal Exposure", SMPTE Journal, Vol. 88, No. 8, August 1979, pages 533-537 (hereinafter referred to as the L Zwick publication) and specifically pages 536-537 thereof.
In certain extreme situations with worsening exposure conditions than that illustratively described above, the lighting conditions may, for all practical purposes, totally frustrate the ability of even a skilled photographer to produce a picture of merely acceptable quality. In these situations, photography would be essentially impossible. For example, consider the same low-light scenario above but where the photographer desires to use a lens that has a relatively large focal length, e.g. a telephoto lens, to capture a scene. For a given film size, the depth-of-field varies in proportion to the square of the focal length of the lens and hence significantly decreases with increases in focal length. Therefore, the depth-of-field provided by such a lens, for certain lens apertures, may not meet the scene requirements. Large focal length lenses also tend to be bulky, massive and relatively heavy and thus, once mounted to a hand-held camera, are hard to hold steady for even moderate shutter speeds, such as 1/30 or 1/60th of a second. Accordingly, to avoid significant camera shake, the slowest shutter speed at which these lenses can be used, without a tripod, is often quite limited. Moreover, since physical limitations on lens size often prevent a large focal length lens from being constructed with large lens aperture sizes, this forces the use of increasingly long shutter speeds to achieve a proper exposure under low-light conditions and exacerbates the need to use other techniques, such as a tripod, auxiliary light source or a faster speed film, to provide usable lens aperture and shutter speed settings that will provide a proper exposure. In the absence of using a tripod or an auxiliary light source, which--owing to the amplitude fall-off as the inverse square of distance to the subject--becomes ineffective at large subject-to-camera distances, or the ability to change to and/or even the availability of sufficiently fast films that exhibit low graininess during the printing process, low-light photography with large focal length lenses is oftentimes practically impossible.
Therefore, as one can now appreciate, even a skilled photographer often experiences difficulties in choosing the proper photographic settings under certain lighting conditions, e.g. lens aperture and shutter settings, selection of lens focal length, use and amount of flash illumination. While certain lighting conditions are so extreme that they simply can not be handled by even a professional photographer, the vast majority of scene lighting conditions fortunately do not fall in this category. Nevertheless, some of these latter conditions often present sufficient difficulties to effectively frustrate the ability of an amateur photographer to take a picture of acceptable quality. In fact, for many inexperienced amateurs, choosing lens aperture size and shutter speed settings amounts to little more than mere guesswork, through which the probability is high that the amateur will select wrong settings and quickly become frustrated. Frustration, if it occurs sufficiently often, leads to dis-satisfaction, which in the context of an amateur photographer often means that that photographer will simply stop taking pictures and turn to other leisure activities which he or she believes to be less trying and more satisfying than photography. Since