Optical Design value Analysis - NIKON AF-S NIKKOR 14-24mm F2.8 G ED Telephoto[No.033]

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

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 AF-S NIKKOR 14-24mm f/2.8 g wide-angle end (14 mm side), and is a performance analysis article of the telephoto end (24 mm side) of the same lens.

NIKON AF-S NIKKOR 14-24mm f/2.8 g 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.

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 figure shows the optical path of the NIKKOR 14-24F 2.8 telephoto end.

It is a variable magnification type that moves entirely to the subject side and extends the total length.

Longitudinal Aberration

Spherical Aberration, Field Curvature, Distortion

Spherical Aberration , Axial Chromatic Aberration

Spherical aberration is small. It is difficult to correct spherical aberration on the telephoto side because the ray flux is larger, but it is corrected neatly.

In axial chromatic aberration, the g-line (blue) is largely bent from the plus side to the tip at the root and penetrates to the minus side.

In the open state, this reduces the average aberration and reduces the intensity by spreading it, and in the small aperture, the chromatic aberration is cut by the aperture.

This technique is used when the absolute value of axial chromatic aberration cannot be kept small.

Field Curvature

Although the g-line (blue) is largely deviated from the field curvature due to the effect of axial chromatic aberration, it seems that the whole image has been appropriately corrected.

Distortion

In the case of a zoom lens, distortion aberration remains on the minus side at the wide-angle end and on the plus side at the telephoto end, but this lens seems to remain on the plus side only slightly.

Lateral Chromatic Aberration

Let's check the chromatic aberration of magnification. Perhaps it was difficult to correct the c-line (red). It seems that the g-line (blue) is put over it to relax the ill-conceived red chromatic aberration of magnification and change it to purple.

Transverse Aberrations

(Left)Tangential direction, (Right)Sagittal direction

Let's look at it as a transverse aberration.

As for the transverse aberration, there is only a large ternary lens and it is organized neatly.

If we take a closer look, there is a coma aberration in the tangential direction when the circumference exceeds 18 mm, and the residual magnification is a little large, and there is a concern that the MTF will decrease.

Spot Diagram

Spot Scale 0.3 (Standard)

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

Since the sagittal direction in the transverse aberration is well organized, it is a large diameter, but it does not become a V-shaped spot and it seems to be corrected appropriately.

Spot Scale 0.1 (Detail)

This is the enlarged spot diagram with the scale changed.

When the image height of the peripheral part of the screen exceeds 18 mm, the effect of chromatic aberration of magnification appears.

MTF

Maximum Aperture F2.8

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

The MTF of the opening is considerably high up to 12 mm in the middle, and decreases after 18 mm in the periphery due to effects such as coma aberration. However, the degree of coincidence of the top of the mountain is good and it seems to be a photograph with good flatness.

Small Aperture F4.0

Since the effect of coma aberration is cut by squeezing, the mountain is much improved.

There is some improvement after the 18 mm circumference, but the MTF degradation due to chromatic aberration of magnification is not recovered even if it is reduced, so it is somewhat improved.

The range is high enough.

Conclusion

Although there is some difficulty in correction because it is only at the telephoto end side of the super wide-angle zoom, it can be seen that it is covered by skillful technology.

This article ends the analysis of NIKKOR 14-24F 2.8.

The next analysis will continue with the long-awaited New / Old 14-24 comparative analysis.

The previous analysis article, NIKON AF-S NIKKOR 14-24mm f/2.8 g wide-angle end (14 mm side) is here.

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.