SIGMA

Optical Design value Analysis - SIGMA 24mm F1.4 DG HSM Art [No.013]

2022-04-19

This is a performance analysis and review article of the Sigma Art 24 F1.4.

You hardly know how the lenses work, how their performance differs from each other, and the specific differences between them.

Even if you look it up in magazines or on the Internet, you probably only find similar "word-of-mouth recommendation" articles like that.

In this blog, we will examine the history of lenses and their historical backgrounds, while estimating lens design performance based on patent information and actual shooting examples, and analyze lens performance in detail from a technical perspective through simulations.

Professional lens designer Jin Takayama carefully unravels optical characteristics such as optical path diagrams and aberrations, which are not generally visible, and explains the taste and descriptive performance of lenses in a deep and gentle manner.

Please enjoy the special information that you can read only on this blog in the world.

Overview

SIGMA's Art lens series is a flagship model that combines a high-quality appearance with metal parts and high resolution performance.

The 24mm F1.4 DG HSM Art lens introduced in this section is a large-aperture wide-angle lens that boasts extremely high resolution performance.

The 24mm F1.4 is one of the first wide-angle lenses in Sigma's Art large-aperture single focal length series.

It was the first wide-angle lens in the Art series of single focal length lenses, which were sold in the order of 35mm, 50mm, and 24mm, so it can be said to be the first Art lens. In recent years, many zoom lenses have a wide-angle end of 24mm, but does the focal length of 24mm mean that it is so popular among users? It may also be the reason why it is the first wide-angle lens to be commercialized.

This lens is new and you can find information about it here.

Private Memoirs

I personally have a bit of a problem with the 24mm focal length…

Now, continuing from the article on the SIGMA 35mm F1.4 Art, we will analyze the Art series single focal lengths.

This is part of our effort to establish a benchmark for modern optical design values, since SIGMA's Art single focal length lenses are designed based on a very straightforward concept of "performance-oriented, size-neutral" and are therefore easy to use as a benchmark standard.

There are still some lenses in the Art series that we have not yet analyzed, but we would like to analyze the 20mm lens next to complete our analysis and move on to the next series.

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SIGMA 24mm F1.4 DG DN Art

Document Survey

Now, when I looked into the patent literature, I easily found patents that I thought would be relevant since it is a modern product. Several examples of patent application 2016-12034 are similar to the shape of the product, but let's assume example 1 as the design value and reproduce the design data below.

Most of the examples in this patent document were of the floating focus type, which uses multiple lens groups for focusing. The product's website does not describe a floating focus, but since the majority of the examples have a floating focus, we assumed that as the design value.

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

Above is the optical path diagram of the SIGMA Art 24 F1.4.

The lens has 15 elements in 11 groups, 2 aspherical lenses, and 7 elements of special low-dispersion material for good correction of chromatic aberration.

The lens has a large f/1.4 wide-angle aperture, so it has a large number of elements for a lens with a typical focal length of 24mm, but perhaps because it is an early product in the Art series, it has fewer elements and aspherical surfaces than the later 28mm, and its size also gives the impression of being small for Art.

Was this a time when there was still some hesitation in the direction of full performance?

Longitudinal Aberration

Graphs of spherical aberration, image surface curvature, and distortion

Spherical Aberration , Axial Chromatic Aberration

Even though this is an early Art lens, spherical aberration and axial chromatic aberration seem to be well corrected.

Image Surface Curvature

Image curvature seems to be slightly variable. After all, even for Art, it is apparent that they are having a hard time suppressing image curvature in wide-angle lenses.

Distortion

Distortion is a barrel distortion with a slight negative side remaining to be corrected, but personally I am not bothered by it as long as it is less than 2.5%.

Chromatic Aberration

The magnification chromatic aberration seems to be well corrected, but the fluctuation is larger in the high image height region compared to the 28mm analyzed in the previous section.

Transverse Aberrations

(Left)Tangential direction, (Right)Sagittal direction

Although the flare in the sagittal direction is much better corrected than with typical wide-angle large-aperture lenses, it is still large. Sagittal flare is an aberration that improves when the aperture is stopped down, so I personally do not mind this level of flare, but it may be a concern for star photographers.

Spot Diagram

Spot Scale 0.3 (Standard)

Spot Scale 0.1 (Detail)

As you could see in the lateral aberration, the spot is extended laterally due to sagittal flare at high image height.

Even for Art lenses, there seems to be a slight sweetness at the extreme periphery of wide-angle lenses, as expected.

MTF

Maximum Aperture F1.4

The MTF seems to decrease towards the periphery of the image as per the image curvature variation, which is a level of high performance that can only be seen by comparing Art lenses with each other.

Small Aperture F4.0

MTF stopped down to Fno4.0. Image curvature is not improved, but the resolution performance of the photo itself improves to the ideal value level because the height of the peaks is increased.

Conclusion

Even though it is a product of the early series of Art lenses, it is an extremely high resolution lens with no perceptible difference in practical use. Since a little time has passed since its release, the price has also become much more reasonable.

However, the level of resolution is so high that it almost hurts your eyes, and once you use it, you may find that your body is no longer satisfied with the wide-angle end of standard zoom lenses. Please use with caution.

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SIGMA 24mm F1.4 DG DN Art

Sample Picture

If you are looking for analysis information on other lenses, please refer to the table of contents page here.

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