The story of Tamron's all-in-one zoom lenses begins with the AF 28-200mm F/3.8-5.6 Aspherical (Model 71D), an SLR lens introduced in 1992. This lens featured a focal length of 28-200mm and a 7.1x zoom, one of the highest among SLR lenses in those days.
Development of this lens began in 1989, nearly three years prior to its release. The assignment given to the development team was to create a lens of a size that made it easily portable. Indeed, all-in-one zoom lenses with almost the same focal length were already on the market, but they were large and heavy and delivered poor picture quality. All users (especially beginners) found them difficult to handle. To meet this challenge the development team set a goal of creating a lens as small as a cylinder, with a diameter as wide as a cigarette packet. Development began with the creation of a graph paper cylinder of that size as a reference sample.
Because the concept of an easily portable all-in-one zoom lens was without precedent, development was extremely arduous and posed many conundrums for those involved. The development team created many prototypes and tested their resolutions, until a satisfactory optical performance was obtained. Finally, they succeeded in developing a model by applying the expertise Tamron had accumulated through its extensive experience in another of its businesses: designing and manufacturing all-in-one zoom lenses for video cameras. Development also received a boost when the team was successful in mass-producing an aspherical (hybrid aspherical) lens with functions equivalent to those of multiple lenses.
The first 28-200mm F3.8-5.6 zoom lens produced through their efforts was called the Model 71D, every aspect of which incorporated Tamron's unique, creative innovations. The aspherical lenses were arranged in the positions which would permit a reduction in the number of lenses and increase design flexibility, while ensuring more effective aberration corrections. They also incorporated the Triple-Cam zoom system, which enables the cams to zoom and focus within a three-layer lens barrel, and an engineering plastic which protects the complex structure from shocks and helps reduce the weight of the product. In the production process, the optical axis tended to be tilted, and uniform precision was hard to obtain. The development team solved these problems by creating methods for checking and adjusting the precision. After nearly three years of effort, they finally completed a product that was ready to be marketed.
The Model 71D thus released first became a hit in Europe and the United States. It later became popular in Japan, as a revolutionary replacement lens. However, the Tamron development team was not satisfied with this result, because the MOD (Minimum Object Distance) (shortest possible distance between camera’s sensor plane mark and an object) of the Model 71D was still 2.1m. This distance was acceptable for a 200mm telephoto lens, but was unsatisfactory for a 28mm wide-angle zoom lens. Wide-angle photos need to be taken from up close to have the unique quality of exaggerated perspective. The long MOD was all the more problematic because the zoom lens was intended for shooting a variety of objects and scenes in everyday life.