This is a performance analysis and review article of the NIKON AI AF NIKKOR 85mm F1.4D.
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.
Overview
This lens is a large aperture lens of the D series released at the end of the film era (90's).
First, let's look at the history of Nikon's 85 mm f / 1.4 specification lenses.
- Ai Nikkor 85mm F1.4S(1981)5/7
- Ai AF Nikkor 85mm F1.4D(IF)(1995)8/9
- AF-S NIKKOR 85mm F1.4G(2010)9/10
groups/elements
The 85 mm lens of the initial NIKKOR lens seems to have started from the Fno1.8, but the specification of the F1.4 will appear in 1981 as described in 1 item of the list above.
After that, the Ai AF Nikkor 85 mm F1.4D, which has been renewed with the auto focus support described in 2 items, is the lens to be analyzed in this section.
There is IF at the end of the name, which indicates the inner focus.
"Although it has become less noticeable in recent years, the question of" "Is this an AF lens?" "and" "What kind of system is this?" "was a major focus of attention at the end of the 80s, when the introduction of auto-focus lenses was in its infancy."
In NIKKOR, the auto focus support started from the AiAF S series that was released after the middle of 1980, which was the predecessor of the AiAF D series, but the 85 mm F1.4 was not released in this initial series.
In the manual focus era, many mid-telephoto lenses used a method of focusing by moving the entire lens. In the case of a large aperture mid-telephoto lens, the weight of the moving group was too heavy to drive the lens.
For this reason, each company examined the use of IF (Inner Focus), and with this lens, NIKON was finally able to support Auto Focus.
The inner focus is a technology that uses only a part of the lens to focus, reducing the weight of the focusing lens and making it compatible with auto-focus. However, if you focus in a bad place, the aberration variation will increase.
For this reason, we had to wait for nearly 10 years to switch from "Ai AF S" to "Ai AF D" in order to improve the aberration correction technology that can be used as IF.
Note: I've said a lot, but it's all speculation.
Private Memoirs
There is a reason why NIKKOR D Series is often featured in this blog.
This is because it has an orthodox optical design, is inexpensive, and has a good balance of practical and sufficient performance.
To put it simply, should I say, "An optical system I want to include in my textbook?"
However, many of the lenses were produced until nearly 2020, so the fact that they are easily available as used products is a perfect match for the reference products on this blog.
EVEN IF YOU SAY IT'S A MASTERPIECE LENS, IT'S BORING IF IT'S HARD TO GET.
Also, I am thankful that NIKON gives me a name that is easy to understand for each generation.
Just by saying "D" in "Nikkor," you get the impression that you are in the' 90s.
It is the opposite reason to analyze SIGMA's Art series which is modern and pursues performance.
Let's analyze it right away.
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Document Survey
It took some time to investigate.
In the patent document, a drawing representing the content is described on the cover, and I also use that drawing as a clue when searching, but the drawing of this patent was a simple layout drawing, so I missed it.
As a result of thorough investigation, it seems that Japanese Patent Laid-Open No. JPH07-199066 is the patent for the subject lens.
Assuming that Example 1 has been commercialized in terms of appearance and the number of components, the design data will be reproduced below.
Notes!
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 F1.4D.
It is composed of 9 sheets in 8 groups, and it does not seem to adopt aspherical surface or special material.
As I explained before, regarding this lens IF (inner focus) type, specifically, it seems that the focus is adjusted by moving the fourth lens to the eighth lens.
The ninth lens, which is closest to the image sensor, is fixed.
By fixing the final lens, it works as a lid.
It prevents foreign matter such as dust from getting inside and damaging the focus mechanism.
Longitudinal Aberration
Graphs of spherical aberration, image surface curvature, and distortion
When I look at the spherical aberration, it is slightly tilted to the minus side, and it looks like it will be a little tasteful.
In recent years, ultra-high resolution has been required even for bright Fno lenses, but in the middle telephoto (portrait lens) of this era, it was also required to soften the description.
Naturally, this is to emphasize the blur, but in addition to this, there was also a problem with the makeup technique of the time when portrait lenses were not supposed to be "over-shooting" when shooting models.
Another problem is that if the resolution is too high, the focus will be too severe.
We are not in an era where we can automatically focus on the pupils with high accuracy like the current Millless cameras, and since it is film shooting, no one can shoot continuously.
With the opening of the large diameter F / 1.4, it is now up to "luck" whether the focus will be on or not.
If you leave slight spherical or coma aberration, the range (depth) that seems to be in focus will expand as a secondary effect.
The idea of leaving a small amount of aberration in the sense of reducing focusing errors also made sense.
As axial chromatic aberration has a large aperture lens, it feels a little tight compared to modern lenses, but let's check the details on the spot diagram.
Spherical Aberration , Axial Chromatic Aberration
The field curvature is slightly shifted to the minus side, but the spherical aberration is also tilted in the same direction, so it is presumed that the balance is taken.
Field Curvature
The field curvature is slightly shifted to the minus side, but the spherical aberration is also tilted in the same direction, so it is presumed that the balance is taken.
Distortion
The distortion is extremely small. It's almost zero.
Lateral Chromatic Aberration (Magnification Chromatic Aberration)
It seems that lateral chromatic aberrations tends to increase toward the upper end of the graph. It seems to be a little noticeable when it exceeds 12 mm of the intermediate increase height. However, since lateral chromatic aberrations is generally on the small aperture side where it is noticeable, it is a large aperture F1.4 lens, so there is no need to worry about the performance of the small aperture side.
Let's check the details on the spot diagram.
Transverse Aberrations
(Left)Tangential direction, (Right)Sagittal direction
Let's look at it as transverse aberrations.
In the tangential direction, there is a slight coma aberration as in the case of the remaining correction of spherical aberration, but it is a sufficiently clean area considering the specification of the large aperture and the number of components.
The coma flare in the sagittal direction is considerably reduced.
Since the spot does not form a V-shape, it gives a round and gentle impression to the boke, so it is probably pursuing the taste.
To put it in a modern way, I feel that it is similar to the expression "three dimensional hi-fi design" that NIKON announced later when they developed NIKKOR58mm.
You may find it helpful to refer to previous articles on hi-fi design.
Related article: NIKON NIKKOR 58 mm F1.4G
Spot Diagram
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.
It can be seen that the spot image seen with the standard scale has sufficiently high resolution.
It seems that there is no color shift at the center of the color as I was worried about in the axial chromatic aberration section.
Spot Scale 0.1 (Detail)
I feel the good balance even if I see it in the detailed scale display.
As expected, there is a V-shaped spot in the 21 mm corner, but the spot has a Marumi color up to 18 mm around it, and a beautiful bokeh look is expected.
It seems that I don't care about the color shift in the peripheral area as much as I was worried about in the lateral chromatic aberrations section. It is probably a strange balance on the transverse aberrations.
MTF
Maximum Aperture F1.8
Finally, let's look at the results of the MTF simulation.
Compared to modern lenses, it is slightly lower overall, but the matching degree of the mountain position is high, and it seems to be able to obtain a uniform resolution feeling over the entire screen.
In the section on spherical aberration, it was explained that the depth of focus is widened by leaving the aberration. However, if we look at the characteristics of the MTF, the peak becomes wider (it looks like it has become wider) by crushing the mountain a little.
Although the resolution is lower, the peak becomes flat in the focus direction, and the focus range to be resolved is expanded.
I think it is designed with this point in mind.
In addition, since it is a lens in the film age, it is not as easy to stretch (enlarge) as it is now, so even this level of resolution is more than enough, and people who want more resolution should have thought that "it is fine to narrow down".
Small Aperture F4.0
Since it is a large aperture lens, the resolution can be dramatically improved by narrowing it down. The position of the mountain of the corner 21 mm is also improved, and it seems to be a high resolution and uniform description over the entire screen.
Conclusion
I thought it was a large and retro-looking aberration lens, but when I looked at the correction of the sagittal coma flare, it was a really well-designed aberration shape.
Looking at the aberration diagram, I can feel the unique design philosophy that is different from other companies. This is the wonderful thing about NIKON.
It has an aberration feel that is compatible with the "3 d hi-fi design" of modern NIKON. It has a unique expressive power that modern crisp lenses do not have.
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Sample Picture
Example photos are in preparation.
If you are looking for analysis information on other lenses, please refer to the table of contents page here.