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Optical Design value Analysis - NIKON NIKKOR Z 14-24mm F2.8 S Telephoto[No.031]

This is a performance analysis and review article of the NIKON NIKKOR Z 14-24mm F2.8 S Telephoto range

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 article is a continuation of the previous analysis article, NIKON NIKKOR Z14-24mm f/2.8 s wide-angle end (14 mm side). It is a performance analysis article of the telephoto end (24 mm side) of the same lens.

NIKON NIKKOR Z14-24 mm f/2.8 s wide-angle end

Please refer to the wide-angle end article linked above for an overview and bibliographic information.

Then, I would like to check the performance immediately.

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NIKON NIKKOR Z 14-24mm f/2.8 S

Analysis of Design Values

Optical Path Diagram

The above figure shows the optical path of the NIKKOR Z14-24F 2.8 at the telephoto end.

It seems to be the type that the whole extends to the subject side when zooming to the telephoto end.

A high-power zoom lens usually zooms to extend the entire length. A wide-angle zoom lens is contracted at the middle zoom, and there is a type that stretches at the telephoto end and a type that remains contracted, but this lens seems to be a type that simply stretches.

Longitudinal Aberration

Graphs of spherical aberration, image surface curvature, and distortion

Spherical Aberration , Axial Chromatic Aberration

Spherical aberration is well compensated because it is small while leaving some undulations.

Even if you say telephoto end, the focal length is 24 mm, so it is wide angle as a focal length.

However, the axial chromatic aberration is supposed to be smaller with a wide-angle lens, but with this lens, it is at the telephoto end, so there seems to be some residual correction.

(I'm getting confused when I write "telephoto" but "wide angle".)

Since it is a wide-angle zoom lens, of course it should be designed so that the wide-angle end side (14 mm side) is the best, so I think this degree can't be helped.

Even if there is a residual correction, the wide-angle end is simply too good. It has been corrected sufficiently compared with the single focus in the poor film age, so it is not a level at which the difference can be understood in practical use.

Image Surface Curvature

The curvature of field is fully compensated.

Distortion

The amount of distortion is small, but the aberration remains on the plus side, which is rare for a wide-angle lens.

The distortion aberration on the minus side distorts the subject in a so-called "barrel shape". The wide-angle lens is basically barrel shape, so if you put a square object such as a building in the corner of the screen and take a picture, the surrounding area will become a deflated shape.

The distortion on the plus side is "bobbin type". In this case, the peripheral part is stretched, but is there uncomfortable feeling because it is opposite to normal wide-angle lens?

The absolute value is small, so you might not be worried about it, but you confirmed it with a real photograph.

Chromatic Aberration

The chromatic aberration of magnification is corrected as well as the wide-angle end. In general, the wide-angle zoom gives more importance to the wide-angle end for aberration correction, and the telephoto end tends to be a little neglected, but it seems that the telephoto end is also well corrected for aberration.

Transverse Aberrations

(Left)Tangential direction, (Right)Sagittal direction

Let's look at it as a transverse aberration.

In both tangential and sagittal directions up to an intermediate image height of 12 mm is sufficiently corrected, but I think it is a little inferior to the wide-angle end because a little halo occurs in the peripheral part exceeding 18 mm in image height.

Spot Diagram

Spot Scale 0.3 (Standard)

This is the result of optical simulation, but first let's look at the spot diagram.

In the figure of axial chromatic aberration, I was concerned about the aberration of the g-line (blue), but when I see it in the spot, it is diffused appropriately and I am not concerned too much.

It must have been calculated to this extent.

Spot Scale 0.1 (Detail)

This is a scaled up image.

MTF

Maximum Aperture F2.8

Finally, let's examine the results of the MTF simulation.

From the center to the intermediate image height of 12 mm, the performance is so high that it can be mistaken for a single focus.

The position of the mountain is slightly shifted from the peripheral image height of 18 mm to the beginning corner of 21 mm. However, since it is at the corner of the screen, it will not be noticed for a normal subject.

Small Aperture F4.0

If the image is narrowed down to F4, the image height up to 18 mm becomes ideal. Although the gap at 21 mm remains, the height of the mountain is improved, so the effect of image quality improvement by narrowing down can be expected.

Conclusion

Since it is a wide-angle zoom lens, it is natural to focus on the wide-angle end side. However, the wide-angle end (14 mm) was so high-impact and high-performance that I found this telephoto side a little rough.

In other words, it is said that one side is too good to stand out. It has better performance than the single focus of the past, so it can be said that it is high performance enough for practical use.

I'm really looking forward to live-action photos.

Wide Angle End (14 mm) Angle end (14 mm), please follow the link below.

NIKON NIKKOR Z14-24 mm f/2.8 s wide-angle end

Amazon Product Link
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NIKON NIKKOR Z 14-24mm f/2.8 S

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.

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