The Ultimate Guide to the RICOH GR3x 26mm F2.8 vs SIGMA 45mm F2.8 DG DN - Optical Design Value Analysis No.063

This is a performance analysis and review article of the RICOH GR3x 26mm F2.8 vs SIGMA 45mm F2.8 DG DN.

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.


The RICOH GR3x is the standard lens model in RICOH's traditional compact camera series, with a focal length equivalent to 40 mm f / 2.8 full-frame equivalent.

On the other hand, SIGMA 45 mm F2.8 is a Contemporary line lens, but it is actually a small lens developed as a dedicated lens for SIGMA's L mount camera fp.

Is it a coincidence? Around 2020, it seems as if the 40 mm focal length boom is happening, and each company is launching products around 40 mm.

Here is an example of a lens with a focal length in the 40 mm range released around 2020.

  • 2019 SIGMA 45mm F2.8 DG DN
  • 2020 SONY FE 40mm F2.5 G (SEL40F25G)
  • 2021 NIKON NIKKOR Z 40mm F2.0
  • 2021 RICOH GR3x (40 mm Equivalent)

Both the NIKKOR 40 mm F2.0 and the RICOH GR3x are a coincidence until their launch on October 1, 2021.

In this comparative analysis, the 40 mm focal length will be deeply appreciated by comparing and analyzing the SIGMA 45 mm F2.8 interchangeable lens, which was the pioneer of the boom, and the RICOH GR3x, which represents compact digital cameras.

If you have not read the analysis of each lens, please refer to the detailed analysis below.


Private Memoirs

For the enthusiasts who look at this blog, the 40 mm focal length lens is an unfortunate existence, and when you look at it from the side, you may feel that it is a strange lens specification that cannot be mainstream for some reason.

In fact, there was a good reason for his misfortune.

The first reason was that "the Leica's first lens was a 50 mm focal length," as explained in the previous article on RICOH GR3x. In addition, many companies that copied the Leica at that time also developed the 50 mm lens, making it the de facto standard.

The second reason is the rise of SLR cameras.

In a SLR camera, a mirror must be placed between the image sensor and the lens to guide light from the taking lens to the optical viewfinder, and the back focus of the lens must be long.

The amount of back focus required at this time differs slightly from company to company, but around 40 mm is required, so a lens with a focal length longer than 40 mm is easier to secure the back focus (= easier to design).

"Easy to design" means that there are various benefits such as "high performance," "small size," and "low cost."

Because it is easy to design, 50 mm, which is a little longer than 40 mm focal length, is preferred in SLR camera, and ironically, the standard lens of SLR camera which almost destroyed Leica also adopted the lens of 50 mm focal length.

In addition, because of the characteristics of the double Gauss lens, which is often used as a standard lens for SLR cameras, a focal length longer than 50 mm is suitable for a long back focus.

Cost of nineteen seventy This is why, in the early days of SLR cameras, there were many lenses with focal lengths larger than 50 mm, such as 58 mm or 55 mm.

But is there a reason for the strange 40 mm focal length movement in modern times (as of 2021)?

We may be able to approach the mystery by observing the lens performance in detail. Let's start the analysis right away.


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

Since "GR3x lens is APS-C size lens" and "SIGMA 45 mm F2.8 is full size", the size of the image sensor is different.

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 APS-C lens would look like this if it were enlarged for a full-size sensor, and the optical system can be evaluated side by side.

As a note, there is no problem in this evaluation in terms of lens (optical), but as an actual photograph, a camera with a small sensor is inferior to a larger sensor in terms of noise and the number of pixels, so please note that that is not taken into consideration.

Optical Path Diagram

RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

Since it is compared in the same scale, it has the same relation as the actual size ratio.

The RICOH GR3x on the left is an APS-C size image sensor, and the SIGMA 45 mm F2.8 on the right is a full-size image sensor, so the size ratio of the image sensor is about 1.5 times.

The common point between the two lenses is that each uses two aspherical lenses.

Although the composition and the number of pieces are quite different, it has a shape with a sense of familiarity.

Next, in the above figure, the RICOH GR3x, which is originally APS-C size, is enlarged by 1.5 times so that "the size of the image sensor is the same".

In short, this is an image of what it would look like if the RICOH GR3x were a full-size camera.

Now you can compare them on the same scale.

What I want to pay attention to here is the shocking fact that "the lens of RICOH GR3x is one size smaller".

Longitudinal Aberration

RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

Graphs of spherical aberration, image surface curvature, and distortion

Spherical Aberration , Axial Chromatic Aberration

If you look at the spherical aberration, RICOH GR3x is an almost straight line with no peculiarity. On the other hand, SIGMA 45 mm F2.8 is an inverted full collection type in which the middle part bulges a little to the plus side. This is a common way of putting together SIGMA lenses.

Axial chromatic aberration is slightly bigger in RICOH GR3x, but both of them are at a level that is well organized.

Field Curvature

The field curvature is organized differently at the top of the graph, but how it is organized in terms of lateral aberration is an important point, so let's make a final confirmation with MTF.


The distortion, RICOH GR3x, is as small as + 1%. On the other hand, SIGMA 45 mm F2.8 is as large as + 3%, which is a little large for a single-focus lens, and is a standard level for a zoom lens.

Distortion aberration can be easily corrected by image processing, so it may be left to you.

Lateral Chromatic Aberration (Magnification Chromatic Aberration)

RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

In lateral chromatic aberrations, RICOH GR3x is arranged in a way that increases almost linearly toward the upper edge of the graph, i.e., toward the corner of the screen. On the other hand, SIGMA 45 mm F2.8 has a shape that changes its position in the middle of the graph so that the aberration is suppressed evenly over the entire screen.

Transverse Aberrations

RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

(Left)Tangential direction, (Right)Sagittal direction

Let's look at it as Transverse Aberrations.

In Transverse Aberrations in tangential direction (left), RICOH GR3x seems to have less chromatic aberration.

In the sagittal direction (right), SIGMA 45 mm F2.8 is smaller.

Spot Diagram

RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

Spot Scale 0.3 (Standard)

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

As you can see from the horizontal aberration, RICOH GR3x has better alignment in the tangential direction (vertical direction), and SIGMA 45 mm F2.8 has better alignment in the sagittal direction (horizontal direction), so it seems to be hard to tell the difference.

Spot Scale 0.1 (Detail)


RICOH GR3x on the left, SIGMA 45 mm F2.8 on the right

Maximum Aperture F2.8

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

It's a pretty close race, but RICOH GR3x is higher and seems to be in a better position.

Small Aperture F4.0

RICOH GR3x seems to have a better balance when I squeeze it a little.


Surprisingly, the optical system of the RICOH GR3x is extremely compact, but it has the same performance as the SIGMA 45 mm F2.8.

Comparing an APS-C size lens to a full-size lens is a bit of a stretch in real life, so it's a bit of a different matter whether the results here will necessarily show up in the photo.

Since the RICOH GR3x is an APS-C size imaging device, the lens is actually small. For example, the degree of freedom in the configuration of the focusing lens is high. Since there are many design advantages over the full-size, please note that the SIGMA 45 mm f / 2.8 is not necessarily inferior.

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.