AF-S DX Zoom-Nikkor 12-24mm f/4G IF-ED Lens

Among lenses of the new DX Nikkor series specially designed for Nikon digital SLR cameras, the first is small and light, with ultra-wideangle zoom capability. Here, the optical designer behind its development reveals the inside story.

		SATO, Haruo 2nd Design Section, 2nd Development Department, Development Division,Imaging Company Nikon Corporation PROFILE: After joining Nippon Kogaku K.K. (now Nikon Corporation) in 1985 for assignment to what was then the Optical Design Group, Mr. SATO has focused on optical design for cameras. The lenses which he has helped design and develop cover a versatile range, including fisheye, telephoto and high-power zoom lenses. Among them, the AF 28-70mm f/3.5-4.5D, AF 24-120mm f/3.5-5.6D and AF 28-80mm f/3.3-5.6G have made the most lasting impression in his memory. Not surprisingly, he has a passion for photography, and he is enough of an enthusiast to have set up a darkroom at home for developing and enlarging his work. Having enjoyed shooting since the days of the Nikon F2, he has more recently been a devotee of the D100 and COOLPIX 2500, although he has a strong attachment to rangefinder cameras such as Nikon SP. Music is another hobby. He plays trumpet as a member of a band. Aside from design work, he writes the "Nikkor - The Thousand and One Night" series that appears in the "Nikkor Club Quarterly" magazine and website. His analysis and evaluation of various camera lenses makes him a highly credible expert in his field.

SATO, Haruo (S,H): Yes it is. The first in this new series is a zoom lens offering ultra-wideangle zoom capability such as 12-24mm f/4. Interviewer: Why develop and design a series of lenses exclusively for digital cameras? After all, conventional Nikkor lenses can be used with digital SLR cameras like the Nikon DX Format digital SLRs. S,H: To explain the reason, I should start by clarifying the difference in format size (*1) between our silver halide 35mm[135] format cameras and a digital SLR. The format of Nikon digital SLR cameras (Nikon DX Format) size is two-thirds that of the silver halide SLR camera format. Compared to its use with a silver halide SLR camera, a conventional Nikkor lens used with a Nikon DX Format digital SLR camera narrows the picture angle to the picture angle at the focal length increased by a factor of 1.5. This is caused by the difference of format size between the camera types.		A distinctive DX Nikkor features compact, lightweight design. By limiting the use of this exclusive design to digital SLR cameras, we can make the lens 485g (17.1 oz.) light, which could never be attained with a conventional lens designed for 135 format cameras.

S,H: In creating a lens exclusively for digital SLR cameras, decreasing the size of a lens to two-thirds that for a 135 format camera would seem simple. But it is not so simple; there are many things we have to think about, such as back focus restrictions, etc., and that idea would not work. And even if it could work, this method would just make the size of conventional lens smaller but not improve aspects of lens performance such as sharpness or vignetting.
So our idea was to achieve good balance between miniaturization in size and improvement in performance. "By limiting use to DX Format digital SLR camera lenses only, it might be possible to create unprecedented lenses by making the most of their specific characteristics." This is the starting point for development of the DX Nikkor series.

(*1) Format size: The size of lens' image circle projected on the image sensor. DX Nikkor is specially designed for use with the Nikon DX Format digital SLR camera format size, so we do not recommend using DX Nikkor lenses with 135 format cameras.





Apparently, many users of Nikon digital SLR cameras are devotees of photographic quality, such as members of the press or professional photographers.
We are always thinking about how to satisfy those people, so we came up with the idea of creating a lens designed specifically for digital cameras. We couldn't be satisfied with conventional lenses developed for use with both silver halide and digital cameras; we wanted to create a lens exclusively for digital cameras by making good use of our expertise in lens design. The first lens that resulted from this way of thinking is the AF-S DX Zoom-Nikkor 12-24mm f/4G IF-ED.

Distinctive features of DX Nikkor, other than miniaturization in size, are rapid autofocus operation, ultra-quiet operation and great body balance at focusing. These are the happy result of Nikon's exclusive SWM (Silent Wave Motor) for autofocusing, as well as IF (Internal Focusing) design, in which lens groups are divided and only interior lenses move for focusing.		Interviewer: What are the benefits of a lens designed exclusively for digital cameras? S,H: First of all, as I said, the format size of a digital camera is two-thirds that of a silver halide SLR camera, so miniaturization can be achieved. But what we stressed in our pursuits was superior lens performance, specially for digital cameras, although compactness and light weight are among important factors of good lens design. Design focusing on the miniaturization is called "scaling design." We employ "balancing design" methods to create superior lenses designed exclusively for DX Format digital cameras.

S,H: Not only miniaturization, but also taking advantage by limiting use of a lens to digital cameras, for better, well-balanced performance.
For example, we realized excellent focal range specifications from 12mm, which would be difficult to realize with a lens also used with silver halide cameras. We strive for optical design that does full justice to the characteristics of the image sensor. And we have evolved the Nikon standard of optical performance beautifully to work with digital cameras. Since the reflection ratio of the image sensor is high, DX Nikkor makes optimal use of renowned Nikon coating technology to restrain ghost and flare (*2) and improve performance.
The aim of balancing design, then, is not only miniaturization, but overall improvement in lens performance.

(*2) Ghost and flare: Flare is a phenomenon in which back light or strong light causes diffused reflection within a lens and makes the image look hazy. Ghost is a kind of flare caused for the same reasons. The visible phenomenon is a kind of halation of a pile of light sources with the shape of aperture.






S,H: Of course we had many alternatives. A normal zoom lens could have been a suitable lead-off lens for the new series, or we could have stressed aperture rather than ultra-wideangle.
But actually there are many normal zoom lenses in our lineup. One example is the recently introduced AF-S VR Zoom-Nikkor 24-120mm f/3.5-5.6G IF-ED. Currently, the idea that high priority should be made of developing lenses for use with digital cameras is taken for granted. This lens is no exception; it features optical performance suitable for use with digital cameras.
So, we concluded that what was lacking from our lineup was an ultra-wideangle lens.
The 17-35mm zoom and 18-35mm zoom are popular standard lenses for the D1X, D2H or D100. But the picture angle of 17mm is equivalent to the picture angle of 25mm in DX Format. Do you think that they are not wide enough? I, myself, often take pictures and, from the user's viewpoint, prefer ultra-wideangle lens. When I take a picture with a 135 format camera, my preferred picture angle is 17 to 18mm. But I cannot get such picture angles with a digital camera. This has been the source of my greatest dissatisfaction regarding a conventional lens lineup. And I always thought that our customers must share this dissatisfaction.

Interviewer: So you wanted to start the DX Nikkor series with an ultra-wideangle lens, not a normal zoom lens, to fulfill customers' most pressing desires? S,H: Exactly. To tell the truth, I was the one who suggested the 12-24mm f/4 specifications! Of course I also intend to pursue a better aperture in the future, but for the first DX Nikkor lens, I like the appeal of optical performance at its maximum aperture of f/4. This demonstrates the superiority of the new Nikkor series developed for the era of digital cameras. I think this design concept is uniquely advantageous to lenses designed specifically for digital cameras.		Because I have fun taking pictures on my own, I always think from users' viewpoints about what lenses or kinds of performance customers want. This perspective is crucial for me in designing lenses.