..... .... Expanding Horizons In Photography Canon's Ultrahigh-Performance L-Series FD Lenses The Ideal Achievement of Canon's Comprehensive Optical Engineering Capabilities necessary. However, in caused by the different remaining in a lens are To eliminate this objectionable because aspherical lenses are A superb camera body is a practice, it is extremely wa velengths of the incident called "residual" aberrations. feature, asphericallenses designed to compensate for prerequisite for taking difficult to create lenses that light. All these aberrations Distinctive expressive have varying curvatures image disto rtion through the quality pictures. However, can approach the "ideal" in influence each o ther in nuances, such as softly which permit all incident use of ideal lens shapes. no matter how superb it may performance. Major obstacles complex ways and affect the out-of-fo cus images, are rays to fo cus at one point. Fo r Asphericallens elements also be, the camera body alone in achieving this include ( I ) image-forming performances produced by these residual example, t he FD 8Smm contribute to re ducing the does not suffice. It requires drawbacks attributable to the of lenses. Aberrations aberrations. f/l.2l short-telephoto lens, overall le ns size. For example, equally superb matching spherical c urvatur~ s of the featuring an extremely large the FD 14mm f/2.Sl uses an interchangeable lenses. elements, (2) pro blems fll.2 maximum aperture, asphericallens element wi th Canon's'\.! I tra-high­ ari sing fro m lens materials, Spherical aberrations are uses an aspherical element an extremely accurate performance l-series FD and (3) problems caused by Spherical aberrations, visible caused by spherical ele ments as its second element. The aspherical shape for the fro nt lenses have been developed as vary ing refractive indexes as flares, caused by spherical in the follo wing manner. lens enjoys an established first surface of its second lens the ideal and ultimate and the wavelengths of lenses affect picture clarity. Incid ent light coming from a reputation for its capabilities element. This element has achievements of Canon's various colors of incident This becomes a major subject, and travelling along to shoot high contrast made it possible to achieve a longstanding expertise in light. Any differences caused problem for fast lenses with the lens's optical axis, does pictures up to its maximum compact lens design; altho ugh optical engineering. by conditions such as those large apertures such as f/l.2. not converge at a single foool aperture. This is attributable it is a super wide-angle lens mentioned above between the Some of the l-series lenses point on the optical axis after to the asphericallens (with an extremely wide Each lens has been developed "ideal" lens and a lens have eliminated this problem passing through the lens, but element. diagonal angle of view of to attain the optical being evaluated are called by using an asphericallens spreads slightly. As a result, (2) Elimination of wide-angle 114°) capable of reproducing performance of the "ideal aberrations. To minimize element. clear images become image disto rtion distortion-free normal images. lens". An ideal lens is an such aberrations, optical Pictures taken using With a large maximum imagi nary lens which meets design theories have been aspherical wide·angle lenses aperture of f/2.8, its the following three optical established. The l -series FD have no disto rtio n even in maximum outer diameter preconditions essential for lenses have been developed to their peripheries. This is measures a mere 74mm. the ideal reproduction of achieve the Ultimate in picture subjects: (I) a dot correcting these aberrations. should be depicted as a dot, These lenses embody (2) a plane should be advanced o ptical concepts depicted as a plane, and (3) and are backed by excellent the picture should be a precision processing. They perfect reproduction of the use special lens materials, and subject with respect to its special asphericallens shape. The "ideal" lens elements, fluorite lens meeting all these elements, and UD glass requirements reproduces the elements. Consequently subject to perfection. To they give extremely high achieve high-performance performance. The designation ,,~~ lenses which can rival their " L" for Canon L-series impossible to obtain. In other viewed through a veil, since "ideal" counterparts in ultrahigh-performance lenses wo rds, incident light o f they lack definition. In optical capabilities, close stands for "luxury" and is different wave lengthS part icula r, 11l'lJ&...:lportun;: methodological studies of indicative of tho utm o~ t converges at different places lenses generate much flare o pticlll theories become aspiration to the "ideal lens" . on the optical axis depending due to large differences in on where it entered the lens the refractive indexes of their surface, at the periphery or cent ral portions and expresses subject depth. at the lens center. Thus, peripheries. Smaller apertures Asphericallenses eliminate In general, zoom lenses tend images formed by incident produce less flare. However, pin cushioning and to show barrel distortion as light rays which pass near the when using larger apertures, barrel-form distortion which zooming approaches the o ptical axis are surrounded greater flare is inevitable. To is found in photographs taken wide-angle end while pin by images fo rmed by other thoroughly solve this using conventional wide-angle cushion distortion increases rays which pass through the problem, asphericallenses and short focal length zoom at the telephoto end. Since lens periphery. This results have been developed with lenses. asphericallenses eliminate in what is called "flare". special surface curvatures, to these types of distortion, Pictures dis playing flare can make all incident rays I)icture distortion refers to a they are used in the super appear rather flat as though converge at one pOi nt. phenomenon in which the wide-angle lenses, wide-angle photograph does not lenses, and wide-angle zooms Aspherical element Fluorite dement accurately represent the in the L-series product line. Most lenses have curvatures subject. For example, a Using aspherical elements in Asphericallenses exhibit which represent sections of square plane fig ure may be its wide-angle zooms, Canon image area. In practice, several excellent optical spheres. In contrast, imaged like a pin cushio n or has led in the application of Ther.e are roughly two types different photographic characteristics which are asphericallenses have peculiar a barrel shape in the image aspherical elements. Among of aberrations or deviations situations call for a wide extremely difficult to achieve shapes, and specially formed fie ld. Thus, pictures are others, the FD 20 - 3Smm from the "ideal" lenses. range of interchangeable using spherical lenses. These peripheries for optimal distorted even if their f/3.SL incorporates an These are (I) Seidel's five lenses such as wide-angle and include (1) the elimination of refract ion of incident light to sharpness remains completely asp herical ele ment for monochromatic aberrations telephoto lenses making it large aperture spherical prodUce precise convergence. unaffected. The distortion enhanced o ptical and (2) chromatic aberration virtually impossible to aberration, and (2) the Lenses with non-spherical lens dealt with here is, however, performance while at the attributable to different achieve such "ideal lenses" elimination of wide-angle curvatures on their rotation quite different from image same time eli minating wavelengths. since more than the rays in distortion. symmetry are called deformation obtained as a barrel distortion. the vicinity of the optical result of the perspective If an image is form ed in a axis must be used. effect often seen in small area (called "Gauss's In addition, the chromalic wide-angle photographs. This do main") using only the dispersion of the lens is because the distortion is incident rays that are near the ele ments affects their optical cau sed by improper o ptical axis (i.e. rays at very performance. These various re fra ction in the lens while sma ll angles of incidence), aberrations can be d ivided perspective deformation aberrations are scarcely roughly into two categories detectable. If only such based o n how they affect incide nt rays close to the image fo rmation. One refers optical axes could be used, the to monochro matic "ideallens"could be realized. aberrations called "Seidel's However, the requirements for five aberratio ns" (Le. Subiect Lens photographic lenses include spherical aberration, comae, large apertures and an as tigmatism, image field ability to form sharp images, curvature, an d image edge-to-edge, with uniform distortion). The other is brightness over the entire chromatic aberration which is A~rr a tion curve Pin cushion distortion "aspheri cal" lenses. Because entered due to different of the aspherical shape, lens refractive indexes between mass production is peripheral portions and technically d ifficult. central portions. Spherical As phericallens characteristics.: aberration appears as lo w­ Subject (I ) Elimination of large- contrast, flat pictures. In Lens axis aperture spherical aberra­ many cases, sm aller apertures tion correct this condition, but With a large-aperture this inevitably becomes a Optical domain nur the , for the spherical lens, incident light major drawback when optkal axis (GluSS'S dom.',) rays which "''''' nur the optical axis converges at various places pictures require wider depending on where it apertures. Barrel rorm distortion Canon FO in terchangeable lenses accidents, breakdowns, substandard For best results use Canon SLR are designed and manufactured to picture quality, etc. that are camera bodies with Canon FO be used with Canon SLR camera attributable to the use of lenses bodies. When so used, they will give interchangeable le nses of other best optical performance by makes with Canon camera bodies. capilalizing on the superb To make picture-taking your capabili ties incorporated in the lifelong pleasure, remember to use camera bodies.