With the birth of cinema just over a hundred years ago, the progresses made between now and then on the techniques of cinematography have never ceased to amaze audiences. Certainly, many of us could remount moments in our lives when we have felt awed by the movies and satisfied that our money’s worth was redeemed in a flurry of special effects; however, very few of us would be inclined to understand just how much effort was put into designing a very necessary part of any film production: the lens.
Not only is a properly designed lens crucial to the quality of picture, but it could also save valuable time and money for the DP and Producer, respectively. This is especially true for the zoom lens, and serves as a main initiator for the constant research that is going into the instrument.
Unlike fixed focus lenses, zoom lenses are image-forming optical systems which are capable of producing images of different sizes of an object from any definite distance (Clark, 4) How it achieves this effect is by moving groups of lenses within the system in a carefully coordinated fashion, using the lenses to appropriately bend the light and focus for our viewing purposes. As simple as it may sound, the science of zoom lens design is an extremely complicated subject that involves rigorous mathematical calculations that are beyond the scopes of this term paper.
The zoom lens has always been essential and existent all-throughout the history of film and cinematography and it has been used it so many films that can help depict various elements such as character emotion and setting tones. However, in order to provide a general understanding of key aspects in zoom lens design, an attempt will be made to summarize one hundred years of technological advancements. Perhaps the very first hints of a zoom lens may be spotted in an 1834 article from the Proceedings of the Royal Society, by Peter Barlow (Clark, 3).
Barlow noticed that by combining a negative lens (bi-concave lens) with a telescope, which contained positive lenses (bi-convex lens), he could vary the magnification of the viewed object in any proportion while never having to lose sight of the object. Although interesting, this was a discovery made only for applications on a visual instrument, and not one which could be used in combination with the photographic camera. In the 1890’s, the development of the varifocal telephoto lenses produced the first camera-associated zoom-like lenses (Kingslake, 4).
These lenses used a similar two-lens system when compared to Barlow’s, yet they provided more readily varied focal lengths by utilizing a rack and pinion mechanism to control the distance of separation between the two lenses. Unfortunately, these lenses proved to be extremely cumbersome to operate, a possible attribution to its lack in popularity at that time. Not only was the image quality inadequate due to the focusing limitations of the photographic plate, a large bellows extension was required to compensate for the varying image distance during zooms (Clark, 4)
At around the same period in 1902, C. C. Allen took a different approach towards creating a variable-focus lens (Clark, 4). The “Allen lens”, as it came to be known, utilized a three-lens system that contained an axially movable middle lens and two stationary outer lenses. This system was unlike the telephoto lens in that it did not require a bellows extension as its image distance remained identical for two positions of the middle lens.
While there was the presence of focus defects with lens movement beyond these two positions, they were usually tolerable over a narrow range of focal lengths. This narrow focal range inevitably placed great limitations on this system’s zooming capacity. The stage has been set for the two major types of zoom lens that shall remain in constant competition with each other over the next 100 years: Machinally compensated and optically compensated zoom lenses. The telephoto lens could be thought of as the ancestor of all mechanically compensated lenses (Clark, 5).
These lenses are heavily dependent on the use of cams to produce an independent, non-linear relationship between the movements of its zoom elements, which in turn achieve the change in power of the lens and maintain the image at some fixed plane (Clark, 12). On the other hand, the Allens lens could be thought to be the originator of all optically compensated lenses (Clark, 5). These lenses maintained a fixed, linear relationship between the movements of its zoom elements, often though means that directly connect the elements together.
Like the Allen lens, all optically compensated zoom lens inescapably produces focus defects, resulting in a final image which oscillates around a mean focusing position (Clark, 30). With the above designs nowhere near perfect, subsequent improvements in lens design all worked to improve both the zoom range and the correction of lens aberrations. In 1932, the Bell & Howell Cooke “Varo” zoom lens became the first ever true zoom lens developed for 35mm cinematography (Warmisham and Mitchell 339).
The “Varo” was a mechanically compensated zoom lens which used cams to operate a variable three-element system, and provided a maximum 3:1 zoom (40 to 12 mm); however, the design was flawed in that with an increasing focal length, the aperture would decrease, creating difficulties in maintaining corrections (Clark, 6). It was still too early and too ambitious of a move for mechanically compensated zoom lenses to be wielding three elements at a time, and lens designers soon reverted back to using only two zoom elements at a time (Clark, 26).
After a slow start in the 1930’s, optically compensated zoom lenses came zooming back with the announcement of the “Zoomar” lens in 1946, developed by F. G. Back for Zoomar Incorporated (Clark, 8). This lens, made for motion-picture cameras, was in improved optically compensated zoom lens that had five positive-component optical elements, the second and fourth being coupled to move together axially. This arrangement allowed the decrease of image shift that is typical of optically compensated zoom lenses (Kingslake, 5).
Unfortunately, with as many as twenty-two optical elements altogether, the Zoomar lens suffered from an inability to correct for the Petzval sum, a lens aberration which results in a severely curved image plane. As if to answer for this flaw, in 1949 the SOM-Berthiot “Pan-Cinor” lens was introduced (Kingslake, 5). Developed by R. H. R. Cuvillier, this was yet another optically compensated zoom lens; however, it differed from the Zoomar in that instead of using an all-positive lens system, the Pan-Cinor lens coupled a pair of positive components with a negative component in between them (Kingslake, 5).
This simple addition of a negative component provided the necessary correction to lens aberration such as the Petzval sum, and ultimately made the Pan-Cinor lens far superior to the Zoomar lens (Clark, 9). Meanwhile, led by H. Hopkins, the mechanically compensated zoom lenses had their share of progress from 1945-1950 (Clark, 9). H. Hopkins was able to design a system that was basically symmetrical, with two negative middle units which mirrored one another’s movements and two identical, fixed positive outer units, this symmetry greatly aided in the correction of lens aberrations (Clark, 24).
One of the most renowned advances in the field of optically compensated zoom lens was made in 1953 by L. Reymond (Clark, 9). By reversing the powers of the Pan-Cinor lens, he created a system comprised of two coupled negative elements moving with a positive stationary element between them; in addition, Reymond added another stationary positive element to the front of the unit, making it a four-lens optically compensated zoom unit. What this setup was able to achieve was a drastically reduced image plan oscillation as well as four points of correct focus throughout the zoom range instead of the traditional three points (Clark, 9).
This was truly a breakthrough for optically compensated zoom lenses. For the mechanically compensated zoom lens, it had to wait until 1971 for its next breakthrough (Clark, 26). In response to the demands made for a zoom lens optimized with a wider angle of view and shorter working distance, G. H. Cook and F. R. Laurent introduced a three-zoom-element system. This lens was capable of covering the most frequently used focal lengths of the fixed-focus lenses in 35 mm cinematography, and produced comparable image quality to fixed-focus lenses (Clark, 27).
This brings us to the end of a period in zoom lens development in which there is a clear-cut difference between one class of lens versus the other. Although many cinematographers may prefer the sharp focus of the mechanically compensated lens over the simplistic operation of the optically compensated lens, a merging of their best qualities was inevitable in pursuit of perfection (Clark, 28). As the complexity of zoom lens design increased with higher expectations for performance, manual design would no longer suffice.
Soon, lens designers found the perfect solution: the computer. With the progression of zoom lens development into the 1970’s, computer optimization programs became a standard tool for lens designers (Kienholz, 1443). These programs increased the efficiency of lens design drastically, as observed when Kienholz re-designed a 1956 lens using the Grey program on a CDC 6600 computer in 1970. Post-optimization, it was shown that the final lens had 11. 8%, 4. 9% and 9.
7% reduction in lens distortion for the wide-angle, intermediate, and telephoto positions of the zoom lens (Kienholz, 1451). In addition, there were improvements in almost all parameters including lateral color and image quality throughout the zoom range. Computer optimization programs can also be seen to work in tandem with other technological advancements. In the early 1990’s, “aspherical lens” became hot research item due to its exceptional ability to correct aberrations that were commonly associated with conventional spherical lens (Betansky, 657).
The use of aspherics would therefore provide ways to decrease the number of lens elements originally used for the purposes of aberration correction, making a zoom system more compact (Yatsu, Deguchi and Maruyama, 663). At the same time, the design of zoom lenses containing aspherical components became even more complicated due to an increased in design parameters. Here, computer optimization programs were used to analyze the parameters one by one and generate a proper design solution (Yatsu, Deguchi and Maruyama, 663). Today, computer programs have become so powerful that precise prediction of various aberrations is possible (Usui et al.
, 389) These new simulation programs allow DP’s to give input as to what “look” they think the perfect zoom lens should produce while allowing researchers to translate their expectations into technical designs. We have truly arrived at a new era for the design of zoom lens, where lens designers, with help from DP’s, can create very practical technical masterpieces that convey artistic ideas from the director’s mind into the audience’s eyes. Now the a general history of the zoom lens has been provided, now we will be looking at how the zoom lens has been used in film productions.
With its varifocal properties, the original purpose of a zoom lens was to allow cinematographers to use one lens only throughout the entire shooting process, thereby generating more efficiency. However, the ability of the lens to zoom during shots and the visual effects generated in such shots became much more valuable tools for creative directors. Film makers often choose to employ zoom lens due to its ability to relay a sense of realism to the audiences- by zooming in from a distance, it is possible to simulate the effect of watching someone or some act in secrecy.
One example of a film that used this effect extensively is Steven Spielberg’s Munich (2005), which depicted the trauma that hits an Israeli assassin who was seeking revenge from the terrorists responsible from the 1972 Munich massacre. Spielberg and his DP not only used the zoom effect to depict a more realistic fitting sense of espionage, but they also wanted to make the film feel as if it were really taking place in the 70’s. This gave the setting of the film a more authentic feel to the audience. A similar usage of the zoom lens can be seen in Alan Rudolph’s Afterglow (1997).
Being a film with a plot that revolves around adultery and emotions, Rudolph wanted to give his shots a voyeuristic feeling (A Luminous Afterglow). By combining long takes with well-choreographed zoom shots, Rudolph was able to guide the audience through performances developed during the course of a shot and allow them to “watch” the actors, exploring the scenes in ways they would never dare. Perhaps one of the most well-known zoom effects is the “dolly zoom”, or alternatively called the “Vertigo zoom”. This technique was pioneered by Alfred Hitchhock in his classic film Vertigo (1958).
This effect basically stimulates the dizzying sensation of vertigo by zooming in one direction and dollying in another direction (Ashcer and Pincus, 98). In Vertigo, the main character John “Scottie” Ferguson develops a severe case of altophobia. The dolly zoom is used to show an altophobic reaction in Scottie’s point of view to show the audience what the character is experiencing due to his case of vertigo. Thus far, this same effect has been widely popularized in features from the Thriller or Horror genres, commonly used to express extreme emotions of the subjects (Valluri).
Another example is a film again by Steven Spielberg. In Spielberg’s thriller film Jaws (1975), he was able to re-popularize the “Vertigo zoom” in a memorable shot of a dolly zoom into a character’s stunned reaction at the climax of a shark attack on a beach (after a suspenseful build-up). With the widespread application of zoom lenses in the film industry today, it is hard to imagine that even just thirty years ago, it was considered impossible to produce a zoom lens whose image quality is comparable to ones generated by fixed focus lenses (Clark, 2).
Indeed, the application of zoom lens has always been essential and existent all-throughout the history of film and cinematography and it has been used it so many films that can help depict various elements such as character emotion and setting tones. Zoom lenses have come a long way in over a hundred years, and it is without a doubt that with the progression of cinematic technology, even more picture-perfect zoom lenses would be developed to fit the needs of the motion picture production communities. Works Cited Ascher, Steven, and Edward Pincus. The Filmmaker’s Handbook. New York: Plume, 1999 B, Benjamin.
“The Price of Revenge. ” American Cinematographer 87. 2 (2006) 1-3. 6 April 2010 http://www. theasc. com/magazine/feb06/munich/page1. html>. Clark, A. D.. Zoom Lenses, Monographs in Applied Optics Vol. 7. New York: American Elsevier Publishing Company Inc. , 1973. Fumiaki, Usui, Jun Osaya, Ken Ito, And Laurence Thorpe. “A New HD Cine Zoom Lens For Digital Motion Pictures. ” SMPTE Motion Imaging Journal. Oct/Nov (2005): 383-395 Kienholz, D. F.. “The Design of a Zoom Lens with a Large Computer. ” Applied Optics. 9(6)(1970): 1443-1452. Kingslake, Rudolf. “The Development of the Zoom Lens. ” Journal of the SMPTE. 69(1960): 534-544.
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