Sometime ago, Digital Camera Watch published an interview to the Nikon designers of AF-S 105/1.4E in two parts:
http://dc.watch.impress.co.jp/docs/news/interview/1017554.htmlhttp://dc.watch.impress.co.jp/docs/news/interview/1018916.htmlI'm afraid it is too long to translate everything, so I extracted some interesting points. If you have any further questions, please feel free to ask.
Hope this would be of any help.
--105/1.4E was intended as the lens that celebrates the 100th anniversary (in 2017) of the foundation of Nikon company, and originally designed as a 100mm lens. For the coherency in the existing product line, however, it was redesigned as a 105mm one.
--Around the time 58/1.4G was designed, Nikon founded a special project team to analyze the optical characters of the historically renowned lenses of different makes using their original measuring machine called OPTIA. The results of the measurements have been taken into considerations in the design of 105/14E
--Zenji Wakimoto, the legendary Nikon optics designer, decided that the steps of focal lengths should be decided according to more natural transition of the angle-of-view and propounded the 50, 36 (nominal 35), 24, 20mm step instead of Contax’ 50, 35, 25, 21mm step. (At that time, neither made 28mm lenses.) To extrapolate the steps into the longer range, they decided on 85 and 105mm focal lengths.
--The basic concept for the aberration correction of 105/1.4E is similar to that of 58/1.4G and is based on Nikon’s original 3D Hi-Fi concept. However, 105/1.4E was designed to be a little sharper than 58/1.4G when it is set wide open and focus closer.
Nikon thinks that there is no absolute answer to the best balancing point of the aberration correction that satisfy all the users. They will offer lenses with different balances of aberration corrections to choose from.
--The conventional lenses have been designed for the infinity (except for older Micro lenses or special purpose lenses). The subject or the scene at infinity can be considered as 2-D object, so a lens can be designed for the flat subjects. On the other hand, the closer subjects are mostly 3-D (except for the reproduction of documents), and 2-D design doesn’t work well. That’s why they started to design the lenses based on the 3-D concept.
--The resulted optical design of 105/1.4E is the combination of the front converter plus the master lens of a modified Gaussian type which is rather similar to the current super-tele design concept.
--ED elements are employed to correct the chromatic aberration. The ED elements are most effective in the lenses longer than 135mm. So Nikon hasn’t used ED glasses even for the fast mid-tele lenses. Also, the conventional mid-tele lenses are of Gaussian (or its derivative) type, and its convex lenses should be made of high-refractive-index glasses. The refractive index of ED glasses is generally low, which makes it difficult to use in the Gaussian design.
--The aspherical element was not absolutely necessary thanks to its relatively narrower angle-of-view.
--The MTF chart of 105/1.4E tells that the mid-angle area is sharper than the central area, because the main focal point doesn’t always coincide with the center (portraiture, for example).
--That said, they don’t like their lenses to be judged only by the MTF chart.
--The cut out of the round bokeh will show up occasionally, which is inevitable in the combination of (D)SLR and f1.4 lenses.
--Ais 105/1.8 was difficult to convert to an AF lens because the total weight of the optics was too heavy to move them at enough speed. The power efficiency of a supersonic motor is not really high.
--VR function was discarded at an earlier stage of its design process, because they decided that the lens would be too long, fat and heavy to use at reasonable comfort.
