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  6. Tale 23 : AI AF Nikkor 80mm f/2.8S

Dawn of a new era; the day that changed SLR systems Tale 23 : AI AF Nikkor 80mm f/2.8S

Tonight's tale is about a Nikkor lens developed in the early period of the history of Autofocus(AF) system. AF is currently very popular, but 20 years ago, many engineers working for camera manufacturers competed against each other to develop the cutting-edge technology. The first time camera users may not imagine that once camera users had to manually adjust exposure values and focus. At present, film cameras are being replaced by digital cameras. However, any product in any age has to go through the stage of initial creation which involves many engineers' unique thinking, efforts, trials and delight of breakthrough. Tonight, I would like to introduce an engineer, a witness to such a new era, and AI AF Nikkor 80 mm f/2.8S, a fruit of his efforts.

F3AF and AF Nikkor

In April 1983, the then best-selling F3 was redesigned to incorporate the AF system to be marketed as the successor F3AF. At that time, AI AF Nikkor 80mm f/2.8S and AI AF Nikkor ED 200mm f/3.5S were also released simultaneously with a motor and electrical component in the lens system. Up to now, the optical system (glass) had been a key element for interchangeable lenses. Today, however, an electric circuit and motor, optical system, and lens-barrel components have become essential for interchangeable lenses just like "Sanbon no Ya" or the Three Arrows taught by Mori Motonari, a 16th century Japanese warlord, to encourage his three sons to band together and cooperate with each other as three closely joined arrows are harder to break. In this respect, the two AF lenses were ahead of their time, designed with an eye to the future in 20 years. They also rivaled or exceeded the other Nikkor lenses in the design concept to offer the highest possible imaging characteristics. The lens barrel designers and the electrical designers were conscious of the uncompromising demands of optical system designers for better imaging characteristics, while applying their unique ideas to the motor and electric circuit layouts, and making sure that size and usability were similar to that obtained with the other lenses. The AF lenses offered by the competitors of that time had a large square protrusion on a part of lens circumference. In contrast to this, our predecessors all believed that lenses should be cylindrical in design and that lens elements should be entirely encapsulated inside the lens barrel without any protrusion. The Three Arrows, that is, the designers of the lens barrel, electrical components and optical system, worked closely with each other and focused all their ingenuity to create the AF lenses. As you can imagine, the two lenses became the cornerstone of today's AF NIKKOR lenses.

Progress of Development of AI AF Nikkor 80mm f/2.8S

Now, let's see the progress of the development of AI AF Nikkor 80mm f/2.8S. The basic design of the optical system was completed in the summer of 1981. This implies that the design concept and development of AF system were launched long ago. The designer of the optical system was Mr. Daijiro Fujie assigned to the then Optical Section 1, Optical System Department. Mr. Fujie was a very gentle and lively personality. He was interested in photography, and had been passionate about it since his college days; not only he took pictures, but he also developed and printed his photographs to make a calendar by himself every year using black and white pictures. After graduating from the university, Mr. Fujie formed a photography circle with his university classmates and even now continues his photographic work. I joined the circle once, and I recall that all circle members had distinctive personalities, coming from many different business backgrounds throughout the industries closely associated with camera manufacturing. I can remember that I was convinced that Mr. Fujie had a profound knowledge and wide experience of photography in that circle activity. He was also responsible for EL Nikkor, industrial lenses, finder optical systems and even the design of optical systems incorporated in equipment, in addition to camera lenses. In particular, his design of custom-made lenses for equipment was really superb. His achievements in the design led him to win the "Academy Award (Scientific and Engineering Award)" in 2001. Few Japanese engineers have ever appeared on the international stage to win an honorable award for their achievements. In this respect, his award was an honor that reflected well on all Japanese engineers. Mr. Fujie went to Beverly Hills in the United States with his wife, rode a limousine just like a film actor, and received the Academy Award. I can imagine how happy he must have been.

Lens performance and imaging characteristics

Cross section of AF Nikkor 80mm f/2.8

Please allow me to continue with a bit of technical explanation. Take a look at the cross-sectional view. You can see that it is a typical Gaussian lens. However, this is not an ordinary Gaussian lens. One of the most striking characteristics of this lens is the focusing mechanism.

Gaussian lens in general feature relatively smaller aberration fluctuations over various shooting distances owing to the higher symmetry of the refracting power of the lens in reference to the stop. For this reason, little over ten years ago, the majority of micro (or macro) lenses were based on the Gaussian design. However, this lens type had the peculiar characteristic of larger coma and greater spherical aberration in the shorter focusing ranges. Therefore, to achieve higher performance and larger aperture, designers had to further struggle for better ideas. In addition, for AF systems designed with a motor-driven lens, the lens had to be as light as possible for smooth focusing. A solution worked out and applied by Mr. Fujie was a unique rear-focusing design in which only the rear group of elements was used for focusing, while proceeding with the floating correction. This innovation was a breakthrough. The focusing relied on the last convex lens. In practice, however, adjustment of this convex lens alone could not suppress possible fluctuations, especially in the curvature of field and astigmatism. Then, Mr. Fujie came up with the idea of correcting the close-range aberration fluctuation by optimizing the refracting power of individual elements and allowing the concave elements cemented in the rear of the stop to move independently. As far as I can remember, this lens was the first commercialization of a Gaussian lens that adopted the rear focusing design. The invention of Mr. Fujie might have been a little ahead of the times. It was not long before the AF had a heyday. The times caught up with his invention. His design philosophy was incorporated in AI AF Nikkor 85mm f/1.8S and AI AF Nikkor 85mm f/1.4D IF and still lives on.

Let's check what AI AF Nikkor 80mm f/2.8S can do. First, let's see the optical design sheets. This lens features very superior aberration correction and no major shortcomings. First of all, the spherical aberration is small and it is kept undercorrected. Next, although the curvature of field remains slightly on the negative side, the astigmatism is very low. The coma is also significantly reduced and the chromatic aberration is limited to a small range. In addition, the floating correction invented by Mr. Fujie has had an enormous impact. In fact, the astigmatism hardly fluctuates, except the curvature of field at the outermost edges varies slightly in close-up images. This helps achieve high-definition imaging and well-balanced tone reproduction when taking portraits or photographing stationary subjects. This also contributes to the improved imaging of out-of-focus background. Mr. Fujie must have been pursing his goal of achieving ideal imaging characteristics. Mr. Fujie had his own idea about what an ideal photographic lens should do, based on his tastes. I have felt in his report his earnestness in designing this lens.

Now, let's examine the imaging characteristics of this lens based on long-range photos and design parameters. In the long shots taken at maximum through minimum apertures, you can see that the lens provides images so very sharp and well-defined that the f-numbers cannot be identified except in the blurred areas, depending on different field depths. The images show high contrast and are free from any significant flare, and at first glance they appear to have been captured by a Micro NIKKOR.

Nikon F2 AI AF Nikkor 80mm f/2.8S f/2.8 1/60 sec. RDP III
Combination of two images after scanned by LS4000 and retouched
©2004/2005 SATO, Haruo

As the lens aperture decreases, the images tend to turn slightly harder. This suggests that satisfactory results may be obtained by increasing the aperture for portraits while lowering the aperture for landscapes. However, at f/16 to f/32, due to the effects of diffraction, sharpness decreases gradually.

Next, let's check the photographic characteristics with sample pictures. Samples 1 and 2 were taken with the maximum (fully open) aperture (f/2.8) at a shooting distance of 1 to 2 m. Sample 1 was shot with the subject facing the light. As you can see from the reflection of the landscape seen in the pupil of the eye and the eyebrows, it is clear that the lens offers very high resolving power and wide-range tone reproduction. In addition, the unsharp reproduction of hair blending into each other shows that the lens provides satisfactory blurring.

Nikon F2 AI AF Nikkor 80mm f/2.8S f/2.8 1/125 sec. RDP III
Combination of two images after scanned by LS4000 and retouched
©2004/2005 SATO, Haruo

Next, take a look at Sample 2. Sample 2 was taken to evaluate the photographic characteristics when shooting a backlit object. The subject is exposed to very strong afternoon sunlight through a lace curtain.

First, look at the fine soft hairs on the skin and the texture of clothing over the shoulder. You can see superior true-to-original reproduction with a very high degree of definition. Moreover, you can also see that the images are very clear and flare-and-ghost-free even under strong semi-backlight conditions. The image provides rather sharp gradation even under these conditions. I'm sure that this lens is ideally suited for anyone who prefers the best sharpness. However, unfortunately, interchangeable lenses for F3AF cannot be used with any AF cameras other than F3AF, F-501 and F4, and F-601M and digital cameras.

Profile of Mr. Daijiro Fujie

Mr. Fujie was always very spirited, openhearted, and soft-spoken. As soon as the news that he was awarded the Academy Award (Scientific and Engineering Award) spread throughout the company, the telephone on his desk kept ringing. I was told that Mr. Fujie had many calls from female staffers asking, "Can I have the signature of my favorite actor Russell Crowe!" and "Give me snapshots of actor Tom Cruise!" in addition to "Congratulations!" and "You've won it!" This is indicative of the sort of person that Mr. Fujie was. For all staffers, it was of great interest to speculate if Mr. Fujie would appear on the same stage as Academy Award winning actors and actresses. However, the Scientific and Engineering Award-giving ceremony was held on a different day from that of the award ceremony for Academy Awards for actors and actresses. Too bad! The female staffers' wishes could not be entirely granted. However, after coming back home, Mr. Fujie said: "I rode a limousine of the same type as the one that big-name actor rode!" beaming with joy like a boy. He was always full of curiosity and the spirit of inquiry like a boy full of fun and mischief. I am sure that this was the driving force behind Mr. Fujie's enthusiasm for his work and photography.

Note

This issue first appeared in "NIKKOR Club Quarterly" magazine; No. 189 (2004-6-30), published by the NIKKOR Club, and was revised for Nikon's webpage..
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