史上最強のアタッチメントワイドレンズZD WIDE PRO 誕生秘話

May, 08, 2017

2017 年5 月15 日、tokyo grapher からリリースされる史上最強のアタッチメントワイドレンズZD WIDE PRO。

On May 15, 2017, tokyo grapher will release the most powerful ever wide-angle attachment lens, the ZD Wide Pro.
A number of technical (optical) difficulties were encountered in the development process. We asked Mr. Tadashi Kimura, the designer of the lens, to reveal the story of how the lens came to be born.

iPhone 史上最高のF 値1.8 が意味するものとは?
F 値が小さくなることにより、よりクリアでコントラストの高い画像が得られるようになります。但し画像はフレア(全体的に白)っぽくなってしまいます。このフレアを除去する一番簡単な方法はレンズ自体を大きくする事が挙げられます。事実としてiPhone7 も2.2 から1.8 になった事でレンズが大きくなっています。
しかしながら、tokyo grapher はiPhone に装着した際の見た目のバランス、携帯性や使い勝手を考慮したサイズ設計が特徴である為、安易にはレンズのサイズを大きくする事ができません。
本来、光学的には今回のF 値変更(2.2 から1.8)に合わせるにはおよそ2 倍のサイズが必要なんですけどね(笑)。

tokyo grapher のような超小口径レンズの設計では、一眼レフ用の交換レンズと比べて技術的に難しい点はサイズが小さいだけではありません。
一方でiPhone のカメラには絞りがないのでこの回避策が使えません。これはアタッチメントレンズ全てに言える事ですが、光学設計においてこのような逃げ場が無い状況というのはある意味で一発勝負という難しさがあります。
また、F 値が小さくなる(より多くの光を取り入れる)事でレンズの取付位置も一層シビアになってきます。レンズが取り込む光の幅が広がる為、アタッチメントレンズの装着位置が少しでもズレてしまう事で画像の一部が暗くなったりボケてしまいます。
その点tokyo grapher ではジュラルミンの削り出しで作られた金属製のバンパーケースやそれと同等の性能までこだわったイージーフィットマウントは精度が高いので心配ないですね。

tokyo grapher は品質に対して妥協という選択はないです。その品質に対する企画側の熱意と設計者の知見や感性、更には製造サイドとの意見交換を経て始めて正しいモノ作りが出来るのですが、今回はまさにその理想的な工程を踏む事ができたのでtokyo grapher として究極のレンズ(最小サイズ)になっています。

What is the meaning of the f/1.8 value, the best f value in the history of the iPhone?
— As an optical designer, what do you think it means for the iPhone 7/7 Plus to have an aperture value of f/1.8, the best value in the phone’s history?
The smaller the f value gets, the clearer the picture, and the higher the contrast. But with a decreasing f value, you get more flare (whiteness throughout the image). The easiest way to get rid of flare is to make the lens bigger. And indeed the transition from f/2.2 to f/1.8 with the iPhone 7 meant that it has a bigger lens.
Having said that, tokyo grapher’s lenses are designed in consideration of how they look when attached to the iPhone, portability and ease of use, so it’s not so simple to increase the size of the lens.
In most cases, to bring the f value down from 2.2 to 1.8 such as we’ve seen with the iPhone 7 would require the lens size to be doubled, from an optics perspective.
So the main question in the optics design this time round was how to keep the size of the lens as small as possible.

――What was the impact on the attachment lenses? (the reason why manufacturers of attachment lenses around the world have been unable to produce compatible lenses)

tokyo grapher lenses are designed with ultra small aperture lenses, which means they are technically demanding to make in comparison with interchangeable lenses for an SLR camera. And that’s not all: for example, with an interchangeable lens for an SLR camera, even if you get flare in the image you can adjust the stop to get the right light/dark balance. In other words, even if the image is slightly whitish when the stop is open, it can be fixed by closing the stop to some extent.
But with the iPhone there is no stop, so you can’t get round the problem by adjusting it. So with all attachment lenses, you don’t have the luxury of this solution. You have to get round the problem in some other way at the design stage.
And as the f value goes down and more light gets in, the constraints on the lens mounting position become more severe. As the lens takes in light over a broader range, part of the image becomes dark or blurred if there is any slight deviation in the attachment position of the lens.
But as far as this point is concerned, tokyo grapher’s metal bumper case, crafted out of duralumin, as well as the Easy Fit Mount, are both made to such high levels of precision that there is no question that the lens won’t be fitted at the right place.

――So is the new lens slightly larger?
Optical design is a field without limitations. To be honest, I wouldn’t say that this is the ultimate lens from a researcher’s point of view. However, it is the ultimate lens in a sense, given the various conditions it has to satisfy such as the performance and size of the product, and furthermore, it has to have a design amenable to mass production.
For tokyo grapher, compromise is simply not an option. To make the right product, you need to have the quest for quality on the planning side, a knowledgeable and sensitive designer, and exchange of opinions with the manufacturing side. We went through this process in an ideal way this time, and ended up with the ultimate lens for tokyo grapher, with the smallest possible size.
ZD WIDE PRO が目指した画像品質
誤解を恐れずに言うとZD とは厳密には歪みゼロではないのです。これはiPhone のカメラ特性と合致するポリシーなのですが、tokyo grapher も人間の目で見た感覚的な画を重視しています。より自然且つ美しい画というコンセプトでiPhone のカメラは画角や色調を最適化していますよね。tokyo grapher ではそのカメラ特性を活かし、且つワイドで歪みのない画(ZD)を写し出しています。写真は定規で図るものではなく人の目で見るものですから(笑)。

iPhone7 のカメラに最適化しています。iPhone7 のカメラは明るくなった(F 値の変更)だけでなく画角も拡がっています(28mm 相当)。これは光学設計や製造レベルで言うと2ステップ上がった程の進化です。
この進化に対して旧レンズ設計を流用した場合、レンズのサイズを2 倍近く大きくする必要がありましたが、我々はそれができません(笑)。画質はもちろん外観も含めたポリシーを貫く為に完全なる新設計となっています。

The Image Quality Tokyo grapher is aiming for with the ZD Wide Pro
――In optics terms, what does zero distortion (ZD) mean?
At the risk of being unclear, zero distortion doesn’t actually mean absolutely no distortion. At tokyo grapher, we place most importance on how an image looks to the human eye, and this is a policy shared by Apple regarding the characteristics of the iPhone camera. The iPhone camera is designed to create the most natural and beautiful images, and the view angle and color tone are optimized for this purpose. At tokyo grapher we leverage the camera’s characteristics to project wide and distortion free images (ZD). Because photographs are not things to be measured with rulers, but things to be looked at through human eyes (laughs).

――Could you say a little about the new lens?
It’s optimized for the iPhone 7 camera. iPhone 7 cameras not only got brighter (thanks to the change in the f value) but the angle of view also got bigger (28 mm equivalent). This is an evolution of about two steps in terms of optical design and manufacturing level.
If we’d used the old lens design to try to keep pace with this evolution, we’d have needed a lens that was twice as big as before – and we can’t do that! (laughs) In order to keep the lens looking good while of course maintaining image quality, we needed an entirely new lens.

Image Comparison

標準レンズ(広角28mm) Standard lens (wide angle 28 mm)

広角アタッチメントレンズを装着 With a wide angle attachment lens

Zero-Distortion WIDE LENS Pro を装着 With a Zero-Distortion Wide Lens Pro

Introduction of Kimura


Optical designer previously employed at Olympus. Experienced in design, to the level of being commended by the photographers in the Magnum global photography group.
After retirement, appointed as a company activation specialist in Itabashi-ku, which is also the location of the manufacturer of this brand. Itabashi-ku, known as the city of optics since the early Showa era. While small and medium enterprises have been falling out of fashion in recent years, Kimura is working to revive Itabashi as the area for optics.

Reporter’s Impressions

設計士(技術者)と言えば良くも悪くも堅物という先入観があった為、過剰とも言える緊張もあったが無駄な心配でした。研究者から見ると「アタッチメントレンズ=玩具」という部分がどこかにあるのでは?と若干の疑念を抱いて臨んだがそんな発想は一切なく、tokyo grapher の企画や意図を最善の方法で具現化する職人(光学設計士)そのものでした。

Mr. Kimura has a combination of refined skills and experience, the desire to make things, and the flexibility to match the times.
Designers (technicians) are thought of as being stubborn, for better or for worse, so I was probably excessively nervous to speak to him, but my fears were unfounded. I wondered if a researcher might think of an attachment lens as a kind of toy. Though I was worried about that, he didn’t think like that at all, and was rather a craftsman (optical designer) who embodied the planning and intention of tokyo grapher in an optimal way.
In the smartphone market, where technology advances quickly, I learned that people like Mr. Kimura who don’t fit into the framework of an optical designer are indispensable.

Zero-Distortion WIDE LENS Pro