The Tamron Lens Story:
An interview with Tamron’s top execs and optical designers to find out how this fascinating company became a leader in long-range zoom technology
by Jason Schneider
Editor’s Note: Our intent in bringing you this in-depth report is to give you a look inside the technical development of new products and laud the achievements of engineers, scientists and designers who contribute to advances in photography and imaging.
Founder, Mr. Takeyuki Arai
Like many familiar names in the photo industry, the company known to photo enthusiasts worldwide as Tamron was first established back in 1950 when Japan was emerging from the ashes of World War II. Two years later it was officially incorporated as the Taisei Optical Equipment Manufacturing Company, Inc. with a capital of 2.5 million yen, a paltry sum even by the standards of that challenging era. But five years later in 1957 the company was already producing an interchangeable 135mm f/4.5 lens for SLRs, and had developed the “T” mount, a simple, non-coupled screw-mounted lens adapter that qualifies as the world’s first interchangeable mount for SLR lenses. The Tamron brand name, first registered in 1958, was derived from the last name of Uhyoue Tamura, Tamron’s acclaimed optical designer who laid the technical foundation of the fledgling company.
During the 1960s, Tamron steadily expanded its horizons, unveiling one of the first affordable telephoto zoom lenses for SLRs (a modest 95-205mm f/6.3) in 1961, and developing a range of coupled Tamron Adapt-A-Matic interchangeable-mount lenses that provided coupled auto-exposure and metering, It also went into the production of ultra-precision test plates, lenses, prisms, and CCTV lenses, all demanding cutting-edge projects that enhanced its technical core competency. By the ‘70s, the company had developed an even more sophisticated Tamron Adaptall interchangeable mount system with built-in lightweight macro mechanism and a proprietary quick-focus system.
During the 1980s, two key factors converged that were destined to put Tamron on the map, both as a brand name and as a major force for technical innovation. First, the company expanded Tamron USA (established in 1979) and began aggressively marketing the Tamron Adaptall system in the U.S., capitalizing on its advantage of allowing dealers to supply lenses for 200 different SLR models with far less inventory by stocking 15 different interchangeable Adaptall mounts. Then, by 1981 Tamron began a major, long-term OEM project—manufacturing 6X zoom camcorder lenses—that eventually gave the company a leg up in optical innovation. The knowledge base it acquired in making extended-range zoom lenses for video cameras provided Tamron with a crucial edge in creating innovative zoom lens designs and employing new precision manufacturing techniques. The process took over a decade to reach full fruition, but it led to such pioneering developments as hybrid aspherical lens elements using precision molded optical resins, complex multi-cam zoom and focusing helicals injection molded from engineering plastics, and the expanded use of AD (anomalous dispersion) LD (Low Dispersion), and XR (Extra Reflective) glass.
In the words of Hank Nagashima, Tamron’s Senior Managing Director, “At the start of the great paradigm shift to autofocus that began in the mid ‘80s we were competent but hardly cutting edge. We really had no state-of-the-art AF Tamron lenses to offer, and as a result our sales were flat. However, while other optical companies were enjoying a period of robust growth, we were quietly optimizing the performance benefits of hybrid aspherical lenses and refining the production engineering of precision plastic lens barrels. In short, we were fine-tuning all the techniques we had learned in making video lenses, and were busily applying them to the design of advanced new AF SLR lenses. Our pivotal moment finally came in 1991 when we introduced the first compact, lightweight ultra-zoom on the market, the Tamron 28-200mm in Nikon mount, and a year later, in Canon EOS mount.
This was truly a revolutionary product--the first long-range zoom lens to fully exploit the advantages of the stability, precision, light weight, and low-friction characteristics of injection molded engineering plastics, and the first lens in its class to employ hybrid aspherical elements to deliver a wider zoom range along with superior imaging performance at moderate cost. It spearheaded a new generation of zoom lenses and set many if the optical design and construction parameters now used by the entire industry. However, I’m proud to say we never lost the momentum that began with that first breakthrough. The culmination of our engineering thrust is today’s innovative 15X Tamron 18-270mm VC zoom with our proprietary Vibration Compensation system, the new Tamron 10-24mm wide-range ultra-wide zoom, and the new Tamron 60mm F2, the only 1:1 macro for APS-C DSLRs with an F2.0 maximum aperture. These two landmark lenses offer clear proof they we’re still at the forefront of optical innovation. ”
Deep tech: How it works and real-world benefits Hybrid Aspherical Elements: Traditionally, multi-element lenses have been constructed by assembling a number of spherical-section glass elements each of which can be polished to close tolerances using relatively simple reciprocating machines. However, decades ago it became clear to optical engineers that designing a lens incorporating one or more aspherical lens elements, ones having more complex and non-spherical surfaces, would allow them to achieve superior optical correction by reducing residual aberrations, and possibly reduce the n umber of lens elements required as well. This is especially important with long-range zoom lenses where secondary color aberration limits resolution at longer focal lengths, and also with wide-angle zooms and high-aperture lenses in general. The problem is that manufacturing solid glass aspherical elements is extremely labor intensive and time consuming even using state-of-the-art machinery, and as a result, lenses incorporating glass aspherical lenses are very expensive.
Tamron was a pioneer in developing high-volume production techniques for manufacturing hybrid aspherical elements that provide optical benefits similar to all-glass aspherics, but at much lower cost. Basically the technique entails bonding a molded aspherical layer of optical resin to a spherical-section glass element to create a hybrid element. This process requires extremely precise temperature control to ensure a perfect bonding of the two materials; all while maintaining very close physical tolerances. The latest long-range Tamron lenses including the AF28-300mm and the high-performance SP AF28-105mm f/2.8 take the hybrid aspherical process one step further by bonding a specially treated aspherical layer to AD (anomalous dispersion) glass and LD (low dispersion) glass—an even more demanding production process. In general, hybrid aspherical elements have enabled Tamron and other lens makers to achieve lighter, better performing, less costly, longer-range, wider-aperture zoom lenses by reducing the number of elements and increasing production efficiency.
Engineering Plastic Chassis Components: All plastics are not created equal. While they all have plasticity, the ability to be formed and molded, modern engineering plastics provide impressive strength and dimensional stability along with the important benefit of lighter weight (the polycarbonate used is about half the weight of aluminum). The fact that these components can be precision injection molded to extremely tight tolerances, do not require any subsequent machining, and are inherently slippery without requiring any lubrication also make them ideal for manufacturing the complex multi-cam zoom and focusing helicals used in today’s zoom lenses.
The Quad-Cam Zoom Mechanism, Integrated Focus Cam, and Internal Focusing System found in Tamron zoom lenses are all based on the sophisticated use of engineering plastics. An affiliated company, Fine Giken, specializes in fabricating the metallic molds Tamron uses for injection molding precision engineering plastics components such as multi-cam helicals. Other leading optical companies have developed comparable production technologies, and today engineering plastics are widely used in zoom lenses ranging from “kit lenses” sold with entry-level DSLRs to professional lenses of the highest caliber. Vibration Compensation (VC) System: Tamron developed the VC system to provide enhanced handheld field performance at long focal lengths and in response to the in-lens image stabilization systems offered in competitive Canon (IS) Nikon (VR) and Sigma (OS) lenses. Not surprisingly, the first lens to incorporate VC is the remarkable new Tamron AF18-270mm f/3.5-6.3 Di-II VC, which provides a 35mm equivalent focal length of 27mm wide-angle to an amazing 419mm at the long end. To avoid patent restrictions on existing optical image stabilization systems, and striving to advance the technology and its performance, Tamron created its own original design.
The VC system developed by Tamron employs a tri-axial image stabilization system that electromagnetically drives a vibration compensator lens that “floats” on three steel ball bearings. Because the compensator lens is free to move in any direction in its low-friction mount, and the actuator provides improved responsiveness, the system provides theoretical advantages that include enhanced compensation for oblique as well as horizontal and vertical shake and improved follow-up performance resulting in more stable viewfinder images. Since the mechanism is designed to allow parallel shifting of the compensator lens solely by means of electrical control, the mechanical construction is also simpler and more robust, so the lens can be kept as small and light as possible. This is borne out by the fact that the size and weight of the 18-270mm lens are only marginally greater than the Tamron 18-250 without VC. According to Tamron’s engineers, the most challenging problem was developing the algorithms for the software controlling the actuator and the three-coil system. Based on field tests, the VC system provides a 3-4-stop advantage in hand held shooting along with a very stable viewfinder image, a performance that’s on a par with the latest image-stabilization systems used by other leading lens makers.
Obviously, Tamron is not the only optical company, or even the only independent optical company, now producing long-range zoom lenses of remarkable range and image quality at very attractive prices, and the fact that the entire field is fiercely competitive clearly benefits enthusiasts consumers like us. In the future, you may rest assured that Tamron will continue to pursue the mission that has defined the company from its very inception— advancing the state of the most important art of all—the art that captures the image. |
