NIKKOR - The Thousand and One Nights No.36
Nikkor P·C 8.5cm F2
Tonight, I would like to discuss an additional NIKKOR lens for rangefinder cameras following Tale Thirty Four. It is the Nikkor P.C 8.5cm f/2, a legendary lens that contributed to making the NIKKOR lenses known all over the world.
by Kouichi Ohshita
I. Encounter with Mr. Duncan
This lens was made world-famous when Mr. David Douglas Duncan, a photojournalist with an exclusive contract with LIFE magazine, first encountered it. You may already know the story, but please bear with me for just a few minutes to hear an old story.
It was in 1950 when Mr. Jun Miki, also a photographer connected with LIFE magazine, was taking a snapshot of Mr. Duncan with the Nikkor 8.5cm he had borrowed from a friend, a photographer who happened to be visiting him. At that time, Mr. Duncan did not take any special interest in the lens, simply saying "Oh, Japanese Sonnar?" However, later his attitude changed quickly when he was shown the enlarged shot, and he started examining the photo with a magnifying glass. "It's great! Very sharp! Take me to the company at once!"
Then, Mr. Duncan, Mr. Bristol, another FORTUNE magazine photographer, and Jun Miki visited the Ohi Plant of Nippon Kogaku K.K. (the current Nikon Corporation). At that time, Masao Nagaoka, then President of the company, led the three to the lens inspection room and showed them a comparison of performance between the camera lenses carried at that time by Mr. Duncan and Mr. Bristol and the NIKKOR lenses, through a projection inspection instrument. They saw the distinct performance of NIKKOR lenses with their own eyes and purchased NIKKOR lenses for Leica on the spot. Then, carrying the lenses with him, Mr. Duncan went to the battlefront of the Korean War, and subsequently his magnificent photographs taken with the NIKKOR lenses were published in LIFE magazine. This made the NIKKOR lens brand known around the world.
II. Projection inspection method
Are you familiar with the projection inspection method discussed above? Take a look at Figure 1, which illustrates a schematic view of a projection inspection instrument. A test chart lit up with a lamp is projected onto a wall surface, or other appropriate screen, through the lens under test to evaluate the resolving power of the lens based on the degree of blur of the projected image. It is a kind of slide projector with increased accuracy.
Needless to say, the most reliable inspection method for photographic lenses is taking actual shots. In practice, however, the actual shooting requires a series of processes such as taking a photograph, developing the film and printing the photographs, thus lens evaluation requires a considerable investment of time and man-hours. In addition, it involves subjects, lighting conditions, films, development conditions and other factors which can cause difficulties in the evaluation of lenses based on a comparison of performance.
There is another optical inspection method known as "point image inspection," in which an artificial star image created by a collimator is formed on a screen through the lens being tested and the projected image is magnified with a microscope for observation. This method is very advantageous for the inspection of the photographic center, though it requires a massive apparatus called optical bench to precisely rotate the collimator and lens under test to allow inspecting the image periphery, and the operation of the apparatus and analysis of the observed results require experience, technical skills and time.
In contrast, the projection inspection provides the performance of the entire image in an instant, and facilitates the evaluation simply by checking the resolution and the degree of blur of the projected image of the test chart.
Nippon Kogaku K.K. (the current Nikon Corporation) reportedly reached the projection inspection method through a number of trials of various inspection methods for manufacturing photographic lenses. Who originally suggested or invented the method? Some say it was a German engineer working in Japan for technical guidance in pre-war days, though we cannot identify exactly who introduced the method. Whoever it was, the projection inspection method won great popularity as an inspection method for photographic lenses and contributed greatly to the enhancement of lens performance. This method is still used widely by optical apparatus manufacturers at home and abroad as a standard inspection method for photographic lenses.
Thanks to the projection inspection system, Mr. Duncan was able to realize the superiority of NIKKOR lenses at once in the lens inspection room, and individual NIKKOR lenses have been able to offer their own sophisticated capabilities as designed.
III. Lens configuration
Now, let us return to the main topic, the 8.5cm f/2 lens.
As you can see in Figure 2, Nikkor P. C 8.5cm f/2 is a typical Tele-Sonnar type lens composed of five elements in three groups. The 8.5cm f/2 features a single lens replacing the last cemented lens in the 5cm f/2 discussed in Tale Thirty Four. The cemented lens helps improve image flatness in wide-angle lenses, but the 8.5cm lens is composed of five elements, one element less than the 5cm f/2 lens, due to the smaller angle of view. The front groups consist of one convex lens and a three-element cemented lens in the same way as in the 5cm f/2. The Sonnar-type lens configuration features less ghost and provides high-contrast images even in the backlit condition due to the reduced interface with air.
In addition, the Sonnar-type lens configuration is suited for high-speed lenses, as noted in Tale Thirty Two, with superior compensation for spherical aberration and coma over the entire image. The 8.5cm f/2 also offers superior compensation for aberrations and thus, it can provide high-quality pictures with higher contrast even at full-open aperture.
The 8.5cm f/2 was one of the lenses designed originally by Mr. Saburo Murakami after the Second World War, as mentioned in Tale Thirty Four. It is not certain when the design was started, though the design seems to have been initiated immediately after the development of the 8.5cm lens was decided after the war, since the lens was put on sale in 1948. More precisely, the development of the 8.5cm lens (medium telephoto lens) was planned together with that of five other lenses immediately after the war, although the program was launched initially as the development of a compact-sized medium telephoto lens with a larger F-number, and subsequently, the program was changed to develop a lens offering a high-speed of f/2. This may have been due to the strong desire to put the then fastest lens on the market as a marketing strategy. Then, Nippon Kogaku K.K. released the 5cm f/1.4, 8.5cm f/1.5 and other high-speed lenses in succession, thus, the 8.5cm f/2 may have started the trend towards larger diameter NIKKOR lenses.
We were surprised to know that it took only a short period of two years or so until the lens was put on the market despite the changed program, changed design of 5cm f/2 discussed in Tale Thirty Four, and other difficulties during the design phase. We can only admire Mr. Murakami for putting his heart into photographic lenses in those days when lens design was relying on a log table, hand-cranked mechanical calculators, abacuses and other manually-operated tools.
IV. Lens performance
Finally, let us examine the lens performance.
As discussed in the lens configuration section, the 8.5cm f/2 provides high-contrast images with less coma flare even at full-aperture. Sample 1 shows a night scene taken at full-open aperture. I am sure you can see how it delivers a clear high-contrast image. Examining carefully, we can notice a slight chromatic aberration and coma flare and thus some degraded contrast in the highlights at full-open aperture. However, we find that the flare is decreased by stopping down the lens from f/2.8 to f/4, and the possible best performance is attained at apertures of f/4 to f/5.6.
In addition, when shooting at full-open aperture, light significantly falls off around a film corner. When you make use of the lens, you can expect a dramatic effect. However, you are recommended to stop down the lens when you want to obtain uniform images. Reduced light intensity at the periphery levels off along with decreasing flare to an entirely uniform image by stopping down the lens to f/4.
Sample 2 depicts a steam locomotive taken at an aperture of f/5.6. The 8.5cm f/2 is excellent in expressing texture, especially depicting a hard texture like a metal, with the higher resolving power and contrast features. Furthermore, the 8.5cm f/2 assures almost completely compensated distortion despite its being a Sonnar-type, which tends to be an asymmetrical lens. Thus, this lens is ideally suited to shoot hard-edged subjects containing many straight line segments such as railway photos and urban landscape.
Sample 3 shows a photo of a hydrangea. It was taken at full-open aperture to express the softness of plant and the humidity, and also to make up for the low amount of light in the rainy day. The blurring effect of background at the maximum aperture is not favorable, though it is inconspicuous in the scene because the background is depressed.
This comes from the fact that the 8.5cm f/2 involves a larger spherical aberration compared to the latest design lenses, and also that the peripheral blurring is distorted in the form of a rugby ball. The distorted background defocusing would disappear by stopping down the lens to around f/4, and a better out-of-focus background would be achieved through a circular aperture.
To tell the truth, the 8.5cm f/2 was not included in the lenses that Mr. Duncan purchased on the spot in the Ohi Plant where he visited to check the performance of NIKKOR lenses. He purchased the 5cm f/1.5 and 13.5cm lenses. It is somewhat strange that he did not purchase the 8.5cm f/2, even though he was attracted right away by the imaging characteristics of this lens. However, he reportedly decided that, as a photographer, the 13.5cm would be better suited for his occupation rather than the 8.5cm.
Whether true or not, the reputation of the 8.5cm lens would never be shaken by the story that Mr. Duncan did not purchase the lens. A snapshot taken with a certain lens strongly appealed to a professional photographer. We would seldom encounter a lens having such an interesting story. We would like to continually manufacture products that surprise and impress every user just like the 8.5cm f/2.
NIKKOR - The Thousand and One Nights
The history of Nikon cameras is also that of NIKKOR lenses. This serial story features fascinating tales of lens design and manufacture.