Tonight, I'd like to talk about the Ai AF VR Zoom-Nikkor 80-400 mm f/4.5-5.6D ED, Nikon's first interchangeable lens system incorporate a vibration reduction (VR) mechanism to eliminate camera shake or compensate for any movement of the hands when taking a picture. This lens actualized users' dreams of easy shooting of night scenes, sports events, or landscapes without using a tripod. How does the VR mechanism work? Who developed the VR mechanism? What kind of technical innovation helped create the Nikon's first VR mechanism-integrated interchangeable lens? Tonight, let's reveal the secrets of this lens system.
Remove the camera shake! The Lens Incorporating a Vibration Reduction mechanism in optical system Tale 35 : Ai AF VR Zoom-Nikkor 80-400 mm f/4.5-5.6D ED
1. The world's first camera to incorporate the in-lens VR function
You might be interested to know that Nikon was the first in the world to release a 35 mm compact camera incorporating a unique VR lens system that removes camera shake by the shifting some lens elements. That compact camera is the Nikon Zoom 700VRQD, well known to those who are familiar with it. The camera was introduced in April 1994. It was relatively large and high-priced for compact camera and did not become a smash-hit commercial product, though it took extremely great pictures. In those days, it was the only camera that could successfully remove the compact camera's major drawbacks, blurry images and shaking of camera during shooting. At that time, Nikon seemed to be confident that the VR mechanism would be ideally suited for compact cameras. Certainly, picture-takers who did not use SLR cameras were in need of such moderately priced, compact-sized cameras that could just take good pictures without any mistakes. In this regard, the concept of the Nikon Zoom 700VRQD was right. In practice, however, it was ahead of its time. This is evidenced by the fact that now we take it for granted when we talk about compact digital cameras in recent years that they are always equipped with the camera-shake removing features. The approach by the developer of the lens was on target. Now at long last, the times have caught up with the idea of the developer.
2. Description of VR (Vibration Reduction) function
For a detailed description of the VR function, please refer to Nikon product catalogues and many commercially available reference manuals. Here, let me provide a brief description of the operating principle of the VR mechanism.
First, let's discuss what camera shakes mean. At the moment when you press the shutter button, you are likely to push the entire camera downward. As a result, the subject moves primarily in the vertical direction (more accurately, the camera body can move three-dimensionally in all directions) and thus it is captured as a blurred image. This phenomenon is known as camera shake and it is more likely to occur at slower shutter speeds. The VR lens is designed to detect any camera shake with the aid of multiple integrated angular velocity sensors, and can shift some lens elements in the direction compensating for the camera shake, thereby canceling possible movement or blurring of the image captured. Therefore, the challenges to be solved include detecting accurately the direction and extent of camera shake, transmitting the detected data to the lens elements to be shifted, and suppressing possible degradation in performance of the lens to be shifted. The solution for camera shake involves vertical movement (shifting) of a part of the optical system against the optical axis, and thus, the shifting cause aberration due to the decentering of lens. How could the lens decentering be minimized? How could such lens configuration and lens type be developed to successfully suppress the aberration to the minimum possible level? Solutions to these problems depended on the technical skills of the optical system designers.
3. Progress of development
Now, let's see the progress of development of Ai AF VR Zoom Nikkor 80-400 mm f/4.5-5.6D ED. The design of the optical system was completed in 1997. In February of next year, a trial blueprint was released. Then, trial manufacturing, verification tests, and actual photo taking tests were repeated and finally, in November 2000, the lens system was put on the market. The optical design was delegated to Mr. Masayuki Aoki, who was then a member of the Optical Design Group 1 in the Optical Design Department 1. He and I were just about the same age, and he was a close friend and also a good colleague of mine. He made a presentation of the lens system at a conference of the Optical Design Study Group held in 2001. This demonstrates that the lens system was innovative enough to merit presenting a paper at a conference. The designer should have felt very proud, I suppose.
Mr. Aoki was a serious-minded and steady man in the ordinary way, doing nothing in a slipshod way but doing everything based on a logical approach. This character was reflected in his attitude developing optical design, and his honesty was shown in the lens performance. To our regret, he past away while still young. We remember it as clearly as if it just happened yesterday, that all of us working with him shed tears when we heard of his sudden departure. His achievements are distinguished and they are still living on with the Nikkor lenses. He may be waiting and seeing how we at Nikon are doing, I'm sure.
4. Imaging characteristics and lens performance
Take a look at the cross-sectional view. This is a six-group zoom lens system composed of six lens-element groups with the positive element group in the front. The first group is responsible for focusing. The essence of this technical innovation is that the second group (the negative group in the second from the left) is composed of a group of elements fixed in relation to the focal surface. Fixing the second group in particular results in a restricted degree of flexibility in optical system design. Instead, however, it contributed to the creation of the optimal configuration and mechanism for VR. The VR group in this lens system is composed of only a part of the lens elements in the second group. This group of lens elements is designed to shift in the up and down direction for vibration reduction in response to the position detected by angular velocity sensors. For the VR group, occurrence of astigmatism and coma due to the decentering of lens is reduced when the VR function is activated, using a method that allows the principal rays to pass in the vicinity of optical axis, as a rule. In this regard, this lens features the configuration suited for both wide-angle and telephoto. As a result, this lens involves the least performance degradation and assures consistent optical performance at the time of the activation of the VR function. In addition, a total of three elements are made of ED (Extra-low Dispersion) glass, two in the first group and one in the third group. The ED glass in the first group compensates for lateral chromatic aberration in the wide-angle side, and is highly effective for compensating for longitudinal chromatic aberration in the telephoto side. Furthermore, the ED glass in the third group is effective primarily for compensating for longitudinal chromatic aberration in the wide-angle side.
Here, let's examine the imaging characteristics of this lens based on long-range shots, sample photos and design parameters. First, the design parameters are going to be considered to examine imaging characteristics. In the wide-angle side, both longitudinal chromatic aberration and lateral chromatic aberration are reduced and thus provide superior compensation, and astigmatism and curvature of field are also reduced and well compensated. If we point out the drawbacks, a slight chromatic coma remains, though it could be compensated by stopping down the lens a little. In addition, there is a barrel distortion, though it is found at a standard level for this class of zoom lens. Next, for the telephoto side, we immediately notice that longitudinal chromatic aberration is minimal. Furthermore, similarly as in the wide-angle side, astigmatism and curvature of field are reduced and compensation is superior. If we point out the drawbacks, a slight coma remains, and pincushion distortion is seen. However, similarly as in the wide-angle side, these are found at standard levels for this class of zoom lens.
Next, let's examine long-range shots and sample photos. First, on the wide-angle side, sharpness is found satisfactory at full-open aperture, but in a very small peripheral region, image contrast is decreased. Stopping down to f/5.6 to f/8, contrast and resolution are further improved, providing the best image quality. Stopping down to f/11 to 16, the entire image becomes uniform and a high-contrast image quality is obtained, though sharpness decreases gradually as the aperture is increased from around f/16 due to the effect of diffraction. This effect becomes more significant at f/22 to 32. On the other hand, on the telephoto side, starting from the full-open aperture, we see the superior compensation of chromatic aberration, providing well-defined images with satisfactory resolution and contrast and also with a rich color for this class of zoom lens. Stopping down the lens to f/8 to 11 increases contrast, providing the best image quality. Stopping down to f/16 to 32, the entire image becomes uniform, though sharpness gradually decreases due to the effect of diffraction.
Sample 1 was taken at a near-full-open aperture, relatively closer to the wide-angle side, at an intermediate focal length. As can be seen from the representation of people and the cubic effect of the ball, the lens yields satisfactory sharpness. Sample 2 was taken at full-open aperture on the telephoto side. As can be seen from the representation of people and the characters on the clothing, the lens offers satisfactory sharpness. In addition, for this class of zoom lens, Bokeh, defocus characteristics, are also relatively satisfactory. Sample 3 was taken with attention paid to the right timing for taking a good photograph. The strongest point of in-lens VR mechanisms is that makes composing and focusing easier due to the ability to check the VR effect through the viewfinder. This constitutes a very important advantage, especially when taking photos of sports activities when faster shutter speeds are selected to eliminate blurring from the images of the subject. This setting is unlikely to cause any camera shake by nature. More importantly, it is a fact that the subject must be stationary when viewed through the finder for accurately tracing the moving subject and realizing the best composition and focusing. In this regard, the in-lens VR function can play an important role. Not only for professional photographers but also for us, amateur camera users, the VR function can provide a significant help for taking photos at athletic meets or soccer games. For Samples 1 thru 3, moving subjects were selected on purpose, and Sample 3 in particular was taken with consideration given to the composition and the best moment for taking a good picture. As can be seen from these sample photos, the lens with the VR mechanism is very useful.
Profile of Mr. Masayuki Aoki
Mr. Aoki was the picture of honesty. He had a strong moral sense, hating anything that is not fair. We had become friends also privately, and sometimes I had been surprised at finding that he had many interests. He had a special appreciation of music, especially among many of them. He listened to various types of music, from songs of idols in the Showa period (1926-1989) to classical music. "Did Mr. Aoki go to a concert of that idol singer? Is he a groupie of the singer?" His concern about pop stars became a topic of conversation among us. The gap between the usual character of Mr. Aoki and his eager interest in idol singers surprised us. He was also good at magic tricks and he demonstrated his expertise with sleight of hand during employee trips. Mr. Aoki's life was short, but he made the most of it, I'm sure. Mr. Aoki will keep living on among us through his achievements.
This issue first appeared in "NIKKOR Club Quarterly" magazine; No. 201 (2007-6-30), published by the NIKKOR Club, and was revised for Nikon's webpage.
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