This is a performance analysis and review article of the RICOH GR Series LENS.
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
As of this writing (2023), the RICOH GR series is one of the best-selling compact cameras in the world.
Although there are several variations of the GR lens, the 28 mm f / 2.8 conversion focal length is the standard specification.
First, let's look back at the history of the GR camera series.
GR in the film age
In 1994, the first GR was released in the late film era. The initial lens specification was a focal length of 28 mm f / 2.8.
- In this article, this product is described as "Film GR1".
There are several derivatives of the film GR1, but there are three lens specifications: 28 mm f / 2.8, 30 mm f / 3.5, and 21 mm f / 3.5. The lens itself is also sold by Leica Mount.
GR Digital
In 2005, when compact digital cameras were at their peak, the GR Digital series made a comeback. However, the GR Digital series had an image sensor (CCD) size of 1/1.7.
Although this size was somewhat large for a compact camera at the time, it was a small sensor, about 1/6 of the 35 mm film size.
At that time, it was called a unique high-quality compact in the camera market, but successor products were released one after another and loved in the market for a long time.
Digital APS-GR
In 2013, at the height of the digital SLR boom, GR Digital underwent a renewal starting with the fifth generation model.
At that time, we significantly increased the size of the image sensor (CMOS) to APS-C size, which is much closer to the 35 mm film version.
In addition, it means that there is no inferiority to the first film GR, and the name has also returned to "GR".
- In this article, it is described as APS-GR1.
APS-GR1 has the same optical specification of 28 mm f / 2.8 as Film GR in the converted focal length, and APS-GR2 is the same optical system.
Although the APS-GR3 has the same specifications, the optical system has been renewed.
The GR analyzed in this article
This is a list of the main cameras in the RICOH GR series. The year of release and the size of the image sensor are listed.
- 1996 Film GR1*
- 2005 1/1.7 Model GR Digital 1
- 2007 1/1.7 Model GR Digital 2
- 2009 1/1.7 inch GR Digital 3
- 2011 1/1.7 Model GR Digital 4
- 2013 APS-C GR1 (5th generation)*
- 2015 APS-C GR2 (same lens as GR1)
- 2018 APS-C GR3*
*indicates the comparative analysis target this time.
Please note that the product names in this article are slightly different from the official names to avoid confusion.
The original product numbers are Roman numerals (GRII, III), but Arabic numerals (GR2, 3) are used because they are difficult to read. The fifth generation GR does not have a number, but 1 is added for easy reading of the article.
The purpose of this article is to compare and analyze two types of lenses, the original GR in the 35 mm film era and the latest GR in the APS size, and trace the history of the evolution and development of the GR optical system.
Private Memoirs
As this is the first compact camera analysis article, I would like to introduce the circumstances leading to the production of this article.
The reason why we did not cover the compact camera in our blog is because "the configuration drawing (cross-sectional view) is not disclosed".
If the configuration diagram is unknown, it is difficult to determine which values are close to the design values by comparing with the patent information.
A configuration diagram is a diagram of the cross-sectional shape of a lens divided vertically. It is also described in product catalogs, etc. In our blog's lens analysis article, it is always introduced as an "optical path diagram" that also depicts the path of light.
Let's start from there to explain how the convention of presenting a configuration diagram was born in the first place.
The story begins a long time ago (before World War II).
At that time, it was common to have 2 to 6 lenses.
There were also many manufacturers of cameras and interchangeable lenses.
During the post-war reconstruction period, there were many camera and lens manufacturers in Japan, and it is said that there were all A-Z except J, U, and X when the initial letters of their names were listed.
Source: Camera and War by Iwao Ogura
At that time, in order to show off that the performance of the company's lens is better than that of other companies' products, the act of disclosing the lens composition diagram began.
At that time, because the number of lenses was small, it became a standard to say, "Because there is one more lens, it is high-performance," or "Because it is the same shape as that lens, is the performance the same?"
It was not the time when there were many types of lens configurations, so if you are a bit of a fan, you could get a lot of information from the configuration diagram.
Another reason is that cameras at that time were cutting-edge technology, and camera buyers were "experts in cutting-edge technology."
In addition, it was an era when you could buy a house with just one camera, so I think it was also an important factor that the buyer was a serious competitor.
Later, as time went by and cameras became more popular, the use of structural diagrams on compact cameras decreased.
It's because the majority of people don't understand at all even if they look at the composition diagram due to popularization.
And at present, there are few manufacturers that describe the configuration drawing of the compact digital camera.
On the other hand, in the case of interchangeable lens cameras, the culture of displaying configuration diagrams has remained, and our blog has been established based on configuration diagrams and patent information.
To put it the other way around, the analysis of a compact camera whose configuration diagram is not disclosed is very difficult even for our blog, so it is not dealt with in a normal analysis article.
However, this GR series only advocates the high-grade compact, and the lens composition drawing is described on the official homepage.
Thanks to that, this is the first time we have published an analysis article on compact cameras.
Document Survey
Based on the published configuration diagram, we investigated and found that the following patent documents are similar to the product.
Film GR1 Japanese Patent Application JP9-236746 Example 1
APS-GR1 Japanese Patent Application JP2014-126844 Example 1
APS-GR3 Japanese Patent Application JP2019-095607 Example 5
Assuming that these have been commercialized, we will reproduce the design data below.
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
1996 Film GR1
The above diagram shows the optical path of the GR1, a wide-angle lens with a focal length of 28 mm f / 2.8.
Four groups of seven lenses, two aspherical lenses, the lens closest to the subject and the lens closest to the image sensor.
It should be viewed as a three lens configuration consisting of a concave lens, a convex lens, and a concave lens arranged symmetrically around the diaphragm, with one concave lens placed on the subject side.
In our blog, we have analyzed a number of interchangeable lenses for single-lens reflex cameras, but ordinary wide-angle lenses for single-lens reflex cameras "do not have a symmetrical arrangement."
Because there is a mirror to guide light to the viewfinder, the distance from the lens to the image sensor (back focus) must be long. The basis of wide-angle lenses for single-lens reflex cameras is an asymmetrical arrangement called a retrofocus type, in which many concave lenses are arranged on the subject side.
In the past, we have analyzed AiAF Nikkor 28 mm F2.8D, a single-lens reflex lens of the same specification, but you may be surprised by the difference in structure, so please take a look.
Also Read: Ai AF Nikkor 28 mm F2.8D
In addition, I think that many people hear that the wide-angle lens of range finder cameras represented by Leica is small and high-performance.
A rangefinder camera has the same structure as a mirrorless camera. Because the back focus can be made short, it is easy to adopt a symmetrical configuration even with a wide-angle lens. Another important factor for high performance is that it is easy to finish with a small size and high performance.
For the same reason, GR's optical system achieves both miniaturization and high performance.
2013 APS-GR1 (5th generation)
The above diagram shows the optical path of the fifth generation Ricoh GR lens (APS-GR1), which has been digitized and whose image sensor has been expanded to APS-C size.
The specification is a wide-angle lens with a focal length of 18.3 mm f / 2.8, which is equivalent to a focal length of 28 mm when converted to full size.
Five groups of seven lenses, two aspherical lenses, the lens closest to the subject and the lens closest to the image sensor.
If you look at this as well, focusing on the aperture, the concave lens and the bonded lens of the concave and convex lens are arranged symmetrically, and the concave lens is added on the most subject side, which is a nearly symmetrical arrangement.
The total number of lenses is the same for film GR1 and APS-GR1, but it is interesting that the order is reversed in many ways.
2018 APS-GR3
The above figure is the latest optical path diagram of the GR3 lens as of the time of writing (2021). (APS-GR3)
There are 6 aspherical lenses in 4 groups: the lens closest to the subject and the lens closest to the image sensor.
It is said on the official website that they aimed to make it thinner, but you can clearly see that it is thinner than APS-GR1 by reducing one lens.
As a result, if you look at the configuration of the lens with the aperture as the center, you can see that the concave lens and the concavo-convex bonded lens are completely symmetrical and have an "extremely beautiful shape".
As a result of 20 years of research and development of the GR camera, it can be said that we have reached a beautiful "perfect symmetrical arrangement".
Now, the optical designs of today's big companies are designed using monster machines at a level that was called supercomputers a decade ago.
If you look at the way in which the design and development process using the latest modern technology has resulted in the "completion of the 100-year-old theory" of perfectly symmetric configurations, how do you describe this without calling it "providence"?
After seeing the end of such a beautiful shape, the designer must have felt the god of lenses behind the finished section and the soul must have burned out.
- Note: This is a wild guess.
Notes on optical path diagrams
The optical path diagram this time is drawn in free-scale so that each lens fills the screen.
Although the film GR1 and the APS-GR1 are drawn as if they are the same size, please note that since the film GR1 has a larger image sensor size, the size ratio of the APS-GR is about 2/3 and the actual size of the APS-GR1 is slightly smaller.
Comparison of optical path diagrams
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
The above diagram shows the optical path of the RICOH GR series. In the following sections, three graphs are shown side by side.
Longitudinal Aberration
Graphs of spherical aberration, image surface curvature, and distortion
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
Spherical Aberration , Axial Chromatic Aberration
Film GR1
Looking at the spherical aberration, it is a full-correction type that slightly swells to the minus side, but it is corrected to a sufficient level as a compact lens for film.
In addition, when the spherical aberration is set to the full correction type, the effect of increasing the depth of focus can be obtained.
Compared to single-lens reflex cameras, film compact cameras have a simple autofocus mechanism, so their accuracy and response speed are inferior.
Therefore, it is assumed that the shape of the spherical aberration is intentionally determined in order to recover the defects of autofocus by leaving a small amount of spherical aberration and increasing the pseudo depth.
You can get a glimpse of the design techniques for compact cameras in the film age, which is lost now.
The performance of the GR lens in this film era was so highly evaluated that it was sold separately as a Leica Mount lens.
As for axial chromatic aberration, it is inferior compared to modern lenses, but it is a sufficiently high-performance class of lenses in the film age.
APS-GR1
The APS-GR1, which is about 20 years older than the Film GR, is as good as ever. The spherical aberration is a grouping of approximately linear levels.
This may be due to the need for higher resolution lenses to take full advantage of the APS-C-sized high-resolution CMOS sensor.
According to the information on the official site, the image sensor of APS-GR1 is an APS-C size CMOS sensor with 16.2 million effective pixels.
I will omit the calculation formula, but if you compare the resolution required for the APS-C size 16.2 million pixel sensor with the 135 film standard, the APS sensor has about four times higher resolution.
Therefore, the amount of aberration of the lens must also be corrected to a level that matches the four times resolution.
Even so, it is an interesting point of optical design that aberration can be reduced to this extent only by design technology, although the number of components is the same as that of lenses in the film age.
APS-GR3
Despite the fact that it is smaller than the APS-GR1 by reducing the number of lenses by one, the amount of aberration is further reduced.
It is a terrible design ability.
As you know, the main method of autofocus in compact digital cameras is to calculate the contrast value from the image information of the image sensor, determine the focus position, and focus the subject.
Because this method is synonymous with "focusing on the image itself," high-precision focusing is possible.
The design method of "leaving a little spherical aberration ~ unnu ~" as explained in Film Compact must be a technique that will soon be lost in modern times.
Field Curvature
Film GR1
At first glance, the field curvature of the film GR1 appears to be quite harsh, but this is not an unusual amount for this class of lenses in the film age.
As an example, it is an interchangeable lens and the price range cannot be said to be the same, but in the past, we introduced NIKKOR 28 mm F 2.8 as a lens with the same focal length 28 mm f / 2.8 as film GR1, so you will understand if you take a look at them together.
Also Read: NIKON Ai AF Nikkor 28 mm F2.8D
APS-GR1
This lens has dramatically reduced aberrations to the level of "What was the film GR1 lens?" I would like to ask what happened in the 20 years since the launch of the film GR.
APS-GR3
Despite the fact that it is smaller than the APS-GR1 with one less lens, it still feels like it has been brushed up.
Distortion
Because the symmetrical optical system has a characteristic that distortion aberration is small, all lenses are small for the focal length in the wide angle range.
In general wide-angle lenses, the graph is inclined to the negative (left side) and tends to form a shape called a cask-shaped, but in the case of film GR, on the contrary, it is a winding shape that is slightly inclined to the positive side.
However, it is absolutely too small to be seen even in real pictures.
Lateral Chromatic Aberration (Magnification Chromatic Aberration)
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
Film GR1
The lateral chromatic aberrations of film GR1 is so small that it seems a little excessive.
Although the symmetric optical system is easy to suppress lateral chromatic aberrations, I strongly feel the designer's philosophy.
APS-GR1
The digitized APS-GR1 tends to be slightly larger in lateral chromatic aberrations.
I'm just guessing, but lateral chromatic aberrations may leave it to image processing because the aberration is easy to correct by image processing.
The film GR1 is abnormally small and the APS-GR1 looks large, but it is not oversized.
APS-GR3
Although the amount of chromatic aberration tends to depend on the number of lenses, the same level has been maintained despite the reduction of one lens from APS-GR1. I feel the strong commitment of the designer.
Transverse Aberrations
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
(Left)Tangential direction, (Right)Sagittal direction
Film GR1
The spherical aberration and field curvature of the film GR1 tend to fall to the negative side as a whole, and the lateral aberration has a halo (inclination) in both the sagittal and tangential directions to balance the focus in the entire area.
APS-GR1
On the other hand, in the APS-GR1, since spherical aberrations and field curvature are corrected to approximately linear levels, lateral aberrations are also corrected to linear levels.
This is a small optical system with a small number of sheets, but it is surprisingly well-organized.
APS-GR3
In the latest APS-GR3, the change is small, but the linearity is stronger, and you can imagine that the aberration correction has been done without compromise.
It's like I've squeezed out the dried rag with a road roller. It's like I've narrowed it down to something that makes me want to stop and say, "Give me a break."
It is a very unnecessary intervention, but what kind of room for improvement is left in the successor GR4?
The person in charge of designing the next model may be having a stomachache every day.
Spot Diagram
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
Spot Scale 0.3 (Standard)
Now let's look at the optical simulation results, but first let's look at the spot diagram.
Looking at the spot standard scale, each of the three lenses is almost a point up to the image height of 18 mm in the peripheral part, and there is only a slight difference in the film GR1 around the image height of 21 mm in the corner.
Spot Scale 0.1 (Detail)
If you look at the detailed scale, the spot size of the film GR1 is large as a whole, but the spot size of the APS-GR1 is small, showing that it is compatible with high resolution.
Again, if you consider the resolution of the film, the spot size of film GR1 will give you a good picture.
MTF
[Left] Film GR1, [Middle] APS-GR1, [Right] APS-GR3
Maximum Aperture F2.8
Finally, let's look at the results of the MTF simulation.
Film GR1
The peak matches and the height is perfect up to the middle image height of 15 mm. The peak position (focus) is off at the corner image height of 21 mm, but the height is left.
By the way, in the film age, it is a matter of print size, the corners are cut and not printed, so most people never see it for life, so this level is more than enough.
To supplement this a little, the size of 135 film is 36 mm wide x 24 mm long, and the ratio is 3:2.
The other print media (e.g., Service Edition E) is 117 mm wide x 82.5 mm high and has a ratio of 2.8:2, which must match the ratio of the print media, so the corners are cut.
Even though the film is 36 mm wide x 24 mm long, there are errors and variations, so it is doubtful that all cameras are exposed to that size, so there must have been a situation unique to analog that there are fewer accidents if you aim at the inside of the film when printing.
Also, the viewfinder in the film age is a single lens reflex camera, but other than some professional cameras, the field of view is not 100%, so most photographers themselves can't see what is in the corner of the film.
In addition, compact cameras have a field of view of around 70-80%, and they also have parallax problems. They are almost like taking pictures with a can.
Therefore, there is also a reason that it is better to print the inside a little because the photographer does not know what is reflected in the corner of the film.
For all of these reasons, people who leave printing to the store rarely look in the corner.
APS-GR1
All the peaks of the MTFs are within the graph scale. In the actual shooting, there will be no feeling that the peripheral part is out of focus.
In the digital age, it is not necessary to explain the viewfinder situation. In a digital camera, the image from the image sensor is displayed as it is on the LCD monitor or viewfinder, and the same image as the one taken is viewed, so the field of view is almost 100%.
This is a blessing of the digital age.
APS-GR3
The mountain is high to the periphery, and the position has been improved to match well.
APS-GR1 and GR3 seem to be slightly improved in the aberration chart, but I strongly feel the degree of improvement in MTF.
While achieving miniaturization, this degree of improvement is "just wonderful" After all, "there is a good reason for a lens with a beautiful cross-sectional shape".
You may have caught a glimpse of some of the famous designers saying that it is not good to be overly particular about the shape of the lens.
Small Aperture F4.0
There is no doubt that the film GR1 and APS-GR1 have solid performance, but I am impressed with the height and consistency of the APS-GR3's prominent peaks.
The APS-GR3 is designed to deliver even greater improvements in performance when narrowed down.
Conclusion
The 20-year history of development of the GR series of optical systems has been brought to you in a condensed form.
As I mentioned a little in the configuration section, I was impressed by the way the symmetric optical system was developed over a long period of time, but I was also amazed by the fact that it has evolved without any compromises in terms of performance.
The transition to a completely symmetric optical system is like a glimpse of the truth of optical design, and we may have seen the untouchable.
Above all, when I see such a typical product gaining a high reputation in the market, I am impressed that there are really many aesthetic users in the camera market.
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.