Apple SIGMA

The Ultimate Guide to the APPLE iPhone 28mm F1.8 vs SIGMA 28mm F1.8 EX DG - Optical Design Value Analysis No.065

This is a performance analysis and review article of the APPLE iPhone 28mm F1.8 vs SIGMA 28mm F1.8 EX DG

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

The lenses introduced in this article have been individually analyzed in detail in the past, so if you have not read them, please refer to the following.

Also Read: Apple iPhone
Also Read: SIGMA 28mm F1.8 EX DG

The Apple iPhone lens has a full-size equivalent focal length of about 28 mm, and the Fno is F1.8.

This time, it is a plan to compare the smartphone lens analyzed in the past with the full-size lens, but the lens with 28 mm focal length and Fno of F1.8 specification is surprisingly few. there is such a difficult circumstance.

At first, I thought that the NIKKOR 28 mm f / 1.8G would be suitable, but I cannot find a patent that seems to be suitable.

When I search on the internet, I find some articles saying that this is NIKKOR28mm, but all of them are quite different in product and shape, so they don't look the same to me.

If anyone knows the patent document of NIKKOR 28 mm F1.8G, I am looking forward to hearing from you.

So, I decided to compare it with the SIGAM 28 mm f / 1.8, although I know that the time and grade are slightly different.

The Apple iPhone lens analyzed in this article is estimated to be close to the one equipped with the iPhone8 released in 2017, but the SIGMA lens for comparison has a gap of more than 15 years between the release date in 2001 and the release date alone, so please compare it only as a reference.

Private Memoirs

The Apple iPhone lens, which is the subject of this analysis, is an ultra-small image sensor (CMOS sensor) called a "1/3 inch type." On the other hand, the SIGMA 28 mm F1.8 ex, which is the subject of comparison, is a "full size", so the size of the image sensor is greatly different.

The above figure compares the size of a full-sized image sensor with that of a 1/3-inch image sensor used in smartphones and compact digital cameras.

There is no strict standard for the 1/3 inch type, so please look at it as a typical one.

The difference in length and width is about 7 times.

The optical system is proportional to the size of the image sensor, so roughly speaking, the size of the lens should be about 7 times the length or diameter.

The question now is how do you compare this small lens to the big one?

In order to make it easier to compare the lens performance, we have adjusted the scale of the graphs so that they can be compared side by side with the full-size lens.

To express this a little more graphically, the scale of the graph has been changed so that the lens for the Apple iPhone "would look like this if enlarged for a full-size sensor", and the optical system can be evaluated side by side.

The caveat is that lens-wise (optically) there is no problem in this evaluation, but in actual photography, a camera with a small sensor is inferior to a larger sensor in terms of noise and number of pixels.

In addition, it is said that various image processing technologies are used in smartphone cameras, so there may be a slight gap between the image of the performance of the lens itself and the resulting photo.

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 Apple iPhone (left) and SIGMA 28 mm F1.8 EX DG (right).

The displayed ratio is the same as the actual size ratio.

Without further ado, the Apple iPhone lens on the left is so "tiny."

The Apple iPhone lens has a total thickness of about 5 mm, which is natural because it fits inside that thin smartphone.

As expected, it is hard to see, so let's express it by making the size of the image sensor the same.

The above figure shows the optical path of the Apple iPhone (left) and the SIGMA 28 mm f / 1.8 ex (right), enlarged so that the image sensor has the same display size.

Think of it as saying, "What if the iPhone lens becomes a full-size lens?"

If you compare the composition again, the Apple iPhone lens is composed of 6 groups and 6 lenses, and all lenses are composed of aspherical lenses.

On the other hand, the SIGMA 28 mm F1.8 EX has 9 groups of 10 lenses, and the 2 lenses shown in red are aspherical lenses.

Because the SIGMA 28 mm f / 1.8 ex is for a single-lens reflex camera with a mirror, it features a long back focus, which is the distance between the lens and the image sensor.

Apple iPhone is a fixed lens type, so the lens is close to the front of the image sensor.

All six lenses of the Apple iPhone are aspherical, but the fifth and sixth lenses are so menacing that it is doubtful whether they deserve to be called lenses.

As you can see from the SIGMA lens, an aspherical lens for a general camera does not have an irregular shape that can be seen by eye.

This is because the more irregular the shape, the more difficult it is to process, and so on. In other words, the more difficult it is to process, the more expensive it becomes.

The most distorted full-size aspherical lens analyzed in the past is the first lens of the NIKON 14-24mm f / 2.8.

ALSO READ: NIKON NIKKOR 14-24mm F2.8

But the Apple iPhone delivers an inexpensive and distorted aspherical lens, so why is this?

The reason is that they use plastic materials.

The lenses of the Apple iPhone are all made of plastic materials, and although plastic materials have concerns about temperature compensation, etc., they have a high degree of freedom in processing, so they can realize a free shape.

You may think that this technology could be converted to a full-size lens, but looking at the situation of each company, it seems that there are still many issues to be solved to convert to a full-size lens.

On the other hand, even with such a large number of aspherical lenses, the lens thickness is only about half, which is a difficult point in lens design.

Longitudinal Aberration

Graphs of spherical aberration, image surface curvature, and distortion

Spherical Aberration , Axial Chromatic Aberration

Let's start with spherical aberration. The Apple iPhone undulates a few times and packs it into a small average. The more aspherical lenses you have, the smaller the spherical aberration, which is an aberration that is easier to contain.

The SIGMA 28 mm f / 1.8 has relatively straightforward linear characteristics, although it leaves a slight aberration on the negative side.

In axial chromatic aberration, there seems to be not much difference between the two, and I was thinking that the iPhone-lens made of plastic material would be rather disadvantageous, but I can say that it is doing well.

Field Curvature

In field curvature, the Apple iPhone undulates several times, but the average size is small. The SIGMA 28 mm F1.8 has a large fluctuation toward the edge of the screen at the top of the graph, and I feel how difficult it is to make the entire full-size imaging surface, which can be said to be huge, uniform.

Distortion

The distortion of a wide-angle lens usually expands to the minus side and tends to be cask-shaped as a picture, but it is shifted to the plus side in Apple iPhone. Does it become so because aspherical lenses are used a lot?

Lateral Chromatic Aberration (Magnification Chromatic Aberration)

In lateral chromatic aberrations, surprisingly, Apple, which uses a lot of plastic materials, is doing well. Plastic lens materials have limited properties, so they don't have as much freedom as glass, so it is difficult to correct, but it is corrected moderately.

This is also because the lateral chromatic aberrations of the SIGMA 28 mm F1.8 is slightly larger. If you look at the SIGMA 28 mm F1.4 Art, which is a representative example of a modern design, it is easy to see that both are large.

Also read: SIGMA 28 mm F1.4 Art

Transverse Aberrations

(Left)Tangential direction, (Right)Sagittal direction

Let's look at it as Transverse Aberrations.

The SIGMA 28 mm F1.8 is designed to be old, and the price is very reasonable, so it has a pretty wild performance.

The Apple iPhone, on the other hand, appears to be fairly uniform, although the edges of the screen are a bit rough.

Spot Diagram

Spot Scale 0.3 (Standard)

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

The stability of the spot shape of Apple iPhone is amazing.

Spot Scale 0.1 (Detail)

MTF

Maximum Aperture F1.8

Finally, let's look at the results of the MTF simulation.

Apple iPhone seems to have a high mountain overall, but the SIGMA 28 mm F1.8 also has a good matching of vertices, and the overall balance of the screen is excellent.

Conclusion

This time, I will compare the lens for the smartphone with the lens for the full-size At first glance, it may be an impossible and reckless act, but I don't want to say that we won or lost in terms of performance.

We proceeded with this analysis on the assumption that the lens image of the future will be seen beyond the fusion of both technologies.

By arranging the two lenses side by side, wasn't it possible to catch a glimpse of the lens of the distant future?

Again, see below for a detailed analysis of each.

Also Read: Apple iPhone
Also Read: SIGMA 28mm F1.8 EX DG

As an aside, I mentioned Sharp's camera-equipped mobile phone at the beginning. This manufacturer had a really good eye for both LCD TVs and mobile phones, but now it is under the control of a Taiwanese company due to the financial crisis.

On the other hand, we recently developed a smartphone with a Leica lens, and we are developing products that we cannot take our eyes off again, so I would like you to make a stir again.

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.

-Apple, SIGMA
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