This is a performance analysis and review article of the NIKON Ai NIKKOR 85mm F1.4S.
You hardly understand the specific differences in how the lenses work and how their performance differs from each other, do you?
Even if you look it up in magazines or on the Internet, all you will find are similar "word-of-mouth recommendations" and articles like that.
In this blog, while researching the history of lenses and their historical background, we estimate lens design performance based on patent information and actual shooting examples, and analyze lens performance in detail from a technical viewpoint through simulations.
Professional lens designer Jin Takayama will carefully unravel optical characteristics such as optical path diagrams and aberrations, which are generally not visible, and explain the taste and descriptive performance of lenses in a deep and gentle manner.
Now, please enjoy the special information that you can read only on this blog in the world.
This is the first 85 mm f / 1.4 lens for Nikon SLR cameras to be released in 1981.
First, let's look at the history of Nikon's 85 mm f / 1.4 specification lenses.
- Ai Nikkor 85mm F1.4S(1981)5/7This article
- Ai AF Nikkor 85mm F1.4D IF(1995)8/9
- AF-S NIKKOR 85mm f/1.4G(2010)9/10
The 85 mm lens of the initial NIKKOR lens starts with Fno1.8, but the lens of the F1.4 specification is the 1981 listed in one of the items above.
In the past analysis articles, we analyzed the Ai AF85mm F1.4D (the second generation) described in the 2 items that evolved to auto focus support released in 1995.
I thought it was a lens with an old-fashioned taste, but it was an excellent lens leading to the modern 3 d hi-fi design.
In a subsequent article, we analyzed the AF-S Nikkor 85 mm f / 1.4G (3rd generation) described in the 3 items released in 2010, which was the latest at the time of writing (2020). We found that the chromatic aberration was improved mainly due to the effect of the special material, and the balance of the overall performance was optimized, even though the number of constituent lenses increased only by one from the 2nd generation lens.
What is analyzed in this section is the Ai Nikkor 85 mm F1.4S (hereinafter first generation), which can be said to be the original 85 mm F1.4 that was finally released in 1981.
1980, the year prior to the launch of the 85 mm f / 1.4S, was the year of the launch of the NIKON F3, NIKON's last single-digit manual focus model.
NIKON F3 is a wonderful design that combines a retro and rustic mechanical feel with a Showa feel of the near future.
After the NIKON F4, it became a modern design using a lot of curves and large size by auto focus, and I felt the future at that time, but it is not so interesting now.
When I use this lens 85 mm F1.4S, should I use it together with NIKON F3, or should I be the only one who wants to decorate with NIKON F3?
I thought it would be difficult to search for this kind of old and simple lens as there are likely to be many similar patents, but I found it easily when I searched based on the year it was released.
There was no patent document with a similar structure other than Japanese Patent Application Laid-Open No. S57-40218, so I think it is correct.
Although there are four examples, they all seem to have the same configuration and performance. Therefore, assuming that Example 1 has been commercialized, the design data will be reproduced below.
The following design values have been selected and reproduced from the appropriate patent literature and do not correspond to the actual product. Naturally, the data is not guaranteed, and I am not responsible for any accidents or damages that may occur by using this data.
Analysis of Design Values
Optical Path Diagram
The above diagram shows the optical path of the NIKON NIKKOR 85 mm f / 1.4S.
Composed of seven lenses in five groups, it does not use aspherical lenses or special low-dispersion materials.
The 4 lenses closer to the subject than the aperture seems to be a double Gauss lens type at first glance, but if you stick the 2nd and 3rd lenses together, it will be a Zoner type, so it is like a Gauss-Zoner eclectic type.
The Sonner-type lens is characterized by the bonding of three lenses. The structure of the Sonner-type lens is based on an era when coating technology was not yet developed. By bonding the lens surfaces as much as possible, the air contact surface is reduced and the decrease in transmittance is reduced.
On the other hand, since this lens is a lens in the era when multi-layer coating is also common, there was no need to stick it forcibly, so the shape was closer to the Gauss type.
The double Gauss type is perfectly symmetrical near the focal length of 50 mm, and the lens groups before and after the aperture stop are approximately the same size.
However, when the focal length becomes a long focus of 85 mm, the symmetrical configuration gradually starts to collapse, and the front group on the subject side becomes larger than the aperture.
This is exactly the kind of lens arrangement that I often refer to as "big Gauss" or "big head Gauss" for the old mid-telephoto lenses.
Graphs of spherical aberration, image surface curvature, and distortion
I think that the spherical aberration is doing well for a large aperture, but the correction remains at a level not seen even in a zoom lens nowadays. However, since it is a full collection type, it seems that a sufficient resolution can be secured if it is narrowed down one step.
The axial chromatic aberration remains large, and you can expect a pretty tasteful description.
The field curvature is also tilted to the minus side to balance the spherical aberration. However, it seems that the difference between tangential and sagittal is small and a flat focus surface can be obtained.
If there is a lot of this "Asu" component, it will result in the so-called "Guruguru Boke" that is often seen in old lenses. It is an unnatural Boke that spreads out in an arc shape, but it does not seem to be the case.
The symmetrical type, such as the Gauss type, is easy to correct distortion, but it is corrected so beautifully that it is abnormal.
In the case of the Gauss type, when the focal length is about 50 mm, distortion occurs by about -2%, and the distortion aberration is on the plus side of the telephoto lens, so it is easy to make it zero around the middle telephoto of 85 mm, but even so, it is uncomfortably small.
Lateral Chromatic Aberration (Magnification Chromatic Aberration)
Lateral chromatic aberrations is also easy to correct in the symmetrical configuration, but in the middle telephoto, the symmetrical structure is broken, so there is a little bit of correction left. However, this large aperture specification is finished to this level with a small number of sheets, so it can be said that it is doing well.
(Left)Tangential direction, (Right)Sagittal direction
Let's look at it as lateral aberration.
Tangential leaves coma aberration.
When coma aberration remains, the MTF, which will be described later, becomes "sticky". This means that the resolution has decreased, but from a different perspective, it can be said that the depth has increased.
If you use an Fno1.4 lens to suppress aberration, the resolution will improve, but the depth will be much thinner.
In the era of manual focus, there was no convenient function such as enlarged display or pupil AF as in the present day. Therefore, there was also the implication of reducing the number of failed photos due to defocusing by leaving coma aberration and expanding the range of focus.
In this era, it was still technically difficult to suppress aberrations, but it was also thought that it would be better not to suppress aberrations too much with large aperture lenses.
Spot Scale 0.3 (Standard)
The results of the optical simulation will be shown from here, but let's look at the spot diagram first.
The rest of the axial chromatic aberration was large, but the correction balance of the c line (red) was good, so it seems that the nasty red is not very noticeable.
Spot Scale 0.1 (Detail)
When you enlarge it, the roundness of the spot remains, and you can expect a natural blur feeling. I feel something that leads to the modern 3 d hi-fi design explained in the NIKKOR 58 mm F1.4G.
Maximum Aperture F 1.4
Finally, let's look at the results of the MTF simulation.
As you can see in the section on Lateral Aberration, the MTF peaks seem to collapse due to the influence of spherical aberration and coma, but instead, you can see that the edges of the peaks are expanding.
The wider the hem, the greater the depth (the range in which the subject appears to be in focus). This means that the subject appears to be in focus even if the focus is soft.
The whole peak is rather low, but the position is perfectly aligned up to the middle 12 mm image height, and a certain height remains even in the peripheral area, so a flat focus can be obtained over the entire screen.
Small Aperture F4.0
If you narrow it down to F4, you can get enough resolution, but the whole focus seems to shift to the minus side.
You can feel the vestiges of the good old days with this lens, but if you consider the background and the trend of the times, you can see that this lens is well crafted.
There are a lot of risks to get an old lens with a high degree of seriousness like before the war, but with this lens, you can enjoy the taste with a large amount of used lenses and reasonable price.
Example photos are in preparation.
If you are looking for analysis information on other lenses, please refer to the table of contents page here.