NIKKOR - The Thousand and One Nights No.83

A pancake zoom lens for the Pronea S, the woman's Nikon
IX-Nikkor 30-60mm f/4-5.6

Tale 83 continues the story of IX-Nikkor lenses for APS cameras that I began with Tale 75. The Pronea S, Nikon's last APS camera, was called the woman's Nikon. This Tale is about the IX-Nikkor 30-60mm f/4-5.6 developed for the Pronea S.

What sort of camera was the Pronea S? What pancake lens was developed for it? What led to the end of APS? I'll use the IX-Nikkor lens to track the history of the Pronea S.

by Haruo Sato

I. Pronea S development

The Pronea S, launched in September of 1998, was developed primarily for women. It was the world' smallest and lightest SLR and had an innovative design, all characteristics that made it extremely popular for a time. So how did development of the Pronea S proceed? I don't think products were developed by departments or sections at that time, but rather by teams established for each product. The Pronea S was the first camera in the industry to be developed by a team. With this team development system, the team leader has absolute authority and bears all the responsibility. The result is consistent product development based on an unwavering concept and faster development. The overall team leader at that time was Fuyuki Yamakawa and the design leader was Kimio Uematsu. The person in charge of design was Naoyuki Murakami, who is currently Sector Manager for Development Sector, Imaging Business Unit. In preparing for this Tale, I had the opportunity to speak with Sector Manager Murakami about development of the Pronea S.

It seems the idea of the camera had been around for quite some time, and that actual development was triggered by the development of the smaller APS film cassette. The question, "Why can't cameras be smaller when the film cassette is so small?" arose. This simple and natural question became the driving force behind the Pronea S. Work on the Pronea S actually began on June 14, 1996 at a meeting of those most concerned. Can a small, but innovative camera with characteristics that make it a Nikon camera be developed without omitting functions and sacrificing performance? Once this question had been posed by designers, representatives from planning and marketing departments gradually joined in. Finally, at a meeting held on October 31, the seventh such meeting, a basic review of the conceptual design was conducted. Then the real design work began. A team, Nikon's first product team, was officially established in 1996. Work on development of the tentatively named P600 started. First the basic size and design were finalized and then the team began designing the various components to fit in that size and shape. Those of us in optical design were in charge of the viewfinder. Our mission was to position the optics as had been determined without any drop in performance. The person in charge of that was Kouichi Ohshita, my partner in these "NIKKOR The Thousand and One Nights".

So, what type of lens would best serve as the standard for the Pronea S? With which lens would the camera be sold as a set? Naturally, it must be a lens that shares the same concept as the camera, and has a matching design. If a smaller size and weight is the priority, it can be sold with a prime pancake lens. However, in terms of usability, zoom lenses are always preferred. Based on the concept behind the Pronea S, it was decided a zoom lens would be best. Is it possible to develop a zoom lens small enough to be called a pancake lens? That is how work on the design of this pancake zoom lens began. I took on the heavy burden of designing the optics for the pancake zoom lens. APS development proceeded with just a few participants. Put nicely, the work was performed by the cream of the crop. Put less nicely, it was performed with the absolute minimum number of people. Therefore, as the primary designer of the IX-Nikkor, it was only natural that I would be selected.

We began to consider the concept, specs, size, and so on in detail. Initially, specifications were for a 28-60mm f/4-5.6 lens with a barrel half the length of the 20-60mm IX-Nikkor, the shortest at the time, and a diameter that was smaller than the mount diameter. Once again, I had built myself a heavy cross to bear. It was because I felt strongly that the Pronea S needed a pancake lens, and that it should also be a zoom lens. I began developing the lens with this seemingly impossible idea. Eventually, I came up with a design proposal that satisfied me, and joyfully passed it along to the designer of the lens barrel. Several days later, the lens barrel designer came to me with a look of pure dejection. He said, "Mr. Sato, you made the lens barrel too small. I have wracked my brain, but can find no way to incorporate the optics you have designed in the proposed barrel. Zooming will cause the lens groups to jump out of the barrel." I wondered if I'd asked too much... Immediately after that, we went to the team leader. The team leader told us he didn't want to give up on the size, and asked if there wasn't anything we could do. The lens barrel designer said he'd tried his best, but the amount of zoom movement is greater than the shortest total length. He said that if the diameter were not increased to a ridiculous size, he couldn't think of any way to prevent the barrel that has only a single cam from being broken. There was complete silence. The team leader said that a 30-60 mm range would mean 2x zoom and make it possible to maintain the compact size for ease of use, although the angle of view would be a little narrower than it would with a 28 mm focal length. The barrel designer and I looked at each other. "Can it be done?" He said he would give it a try. To this day I remember that conversation. The IX-Nikkor 30-60mm f/4-5.6 pancake lens was ultimately realized by shaving a little off the wide-angle end (the equivalent angle of view in 35mm [135] format was 37.5-75 mm).

The Pronea S and IX-Nikkor 30-60mm f/4-5.6 were released in September of 1998. When production was terminated in November of 1999, total production had reached 189,797 units, just short of 200,000. Also unfortunate is the fact that the Pronea S was Nikon's last APS-format single-lens reflex camera. Just what was the APS system? Thinking about it now, it was a turning point that provided a look into the future. It was the final evolution of the silver halide film system. The APS system advanced the digitization of silver halide prints, and gave birth to the concept of Exif information. Looking back, I can't help but think the technology I considered a flower that never bore fruit was inevitable.

II. Development history and the designer

Let's take a look at the development history through the breadcrumbs of patents and reports. The optical design report for this lens was submitted on November 20, 1996. There were ultimately two proposals, one for a 28-60 mm zoom range and another for a 30-60 mm range. The patent was filed in January 1997 and published in August 1998. The patent also describes examples for a 30-60 mm and a 28-60 mm range of focal lengths. Even at this point we still see evidence of consideration of a 28-60 mm zoom range. Now let's look at drawings and product order files. Trial production began on April 3, 1998. This is the date prototype drawings were released. Mass production drawings were released on May 9, 1998. That means that mass production began sometime in 1998. Roughly one year passed between the start of trial production and the start of mass production. The lens was released in September of 1998 after a short development period of approximately one and a half years. At the time, this was the fastest a new product had ever been made ready for sale. In fact, this short development period even included consideration of a retractable barrel that would further reduce the overall length. However, the trade-off would have been a significant increase in barrel diameter. As the lens was already short, any additional reduction in length would have been insignificant. Therefore, the retractable barrel was abandoned without further pursuit. Production of the lens ended in November of 1999, just before the start of the 21st century. It seems a little like destiny to me. While a small amount of stock likely remained on the market, the discontinuation of sales in 1999 means this lens had an extremely short sales period of about one year.

Now let's take a look at the optical designer. I was the designer. I seem to remember completing the design within one or two days. That is because I also had orders for two other new designs, two or three orders for the start of trial production, and I was responsible for supervising new employees in their on-the-job training. It was probably the busiest time of my career. This lens that I developed during such a busy time was constructed of 6 spherical glass elements made of the least expensive materials available at the time. In addition to being the smallest and lightest zoom lens ever at the time, it utilized the fewest number of lens elements and at the lowest cost ever.

At initial release, the lens alone was priced at ¥20,000 and was also sold as a relatively inexpensive set with the Pronea S priced at ¥74,000.

III. Lens construction and characteristics

First, take a look at a cross-section of the IX-Nikkor 30-60mm f/4-5.6 (Fig. 1). Please forgive me if the following is quite technical.

Let's consider the structure in the order in which light rays pass through the lens from the left. This zoom lens has a typical negative-positive (concave-convex) structure. As you can see, this negative-positive two-group zoom lens has basically the same structure as a retrofocus wide-angle lens. In general, there is a negative-positive subgroup inside the front group of the negative-positive two-group zoom structure. Normally, only the front group is comprised of three or more elements. I developed a lens structure that consolidated the multiple negative elements into a single element and made up for the lost elements with an aspherical surface. I used this structure frequently. However, I believe the IX-Nikkor 30-60mm f/4-5.6 was the first negative-positive two-element lens that did not have an aspherical surface in the front group. Further, the rear group required an Ernostar structure comprised of a minimum of four elements (positive-positive-negative-positive). The IX-Nikkor 30-60mm f/4-5.6 design adhered to common theory with the minimum number of lens elements in its rear group. Therefore, as we can see from Fig. 1, the IX-Nikkor 30-60mm f/4-5.6 has a separate six-element spherical structure, which is the optimal configuration for an inexpensive lens. What's more, the last three elements all come in contact with one another. This not only contributed to a reduction in the number of parts needed, but also simplified the structure of the lens barrel. Most of the glass used was inexpensive glass that could be procured anywhere in the world, allowing for lens production in any country. Only the first lens element was made of a lanthanum (La) glass, which is relatively expensive compared to the other, more conventional glass materials used. Further, taking both the ease with which glass is processed and the cost of glass materials into consideration, the thickness of the lens and its rim also impose restrictions on design. As you can clearly see, this lens was designed with cost reduction in mind. Therefore, even in the 21st century, the IX Nikkor 30-60mm f/4-5.6 can be considered the smallest negative-positive two-group zoom lens designed with the lowest cost possible.

IV. Design performance and evaluation

First let's look at design data. As I have always stated, evaluations are both subjective and relative. Please use my own evaluations merely as reference.

This is a typical negative-positive two-group zoom lens. It is ultra compact with the world's smallest six-element structure that does not utilize aspherical surfaces. You must be thinking there is a drawback somewhere. Let's see what design values have to say.

We'll start with aberration characteristics at the 30 mm maximum wide-angle position with focus at infinity. Spherical aberration is fully corrected. As such, there are fewer lens zones that causes spherical aberration. Coma is not significant, but there is a tendency toward outer coma. Lateral chromatic aberration is well corrected, but some chromatic coma does remain. There is very little curvature of field or astigmatism. Distortion has a straightforward barrel shape, but is significant at -5%. Allowing this distortion helps to control curvature of field and astigmatism. A certain amount of negative distortion also helps to suppress variations in short-distance aberrations, especially with retrofocus lenses. For these reasons, I chose to allow the distortion. And what about those variations in aberrations at short distances? First, curvature of field becomes positive. However, with this lens, the sagittal and meridional image planes cross at a height 70% of the total image height, creating an intersection with no astigmatism. Therefore, curvature of field only turns positive at the outermost edges. Next, coma changes to outer coma. Chromatic aberration balance does not change much, but does become noticeable as outer coma increases. Distortion increases to -7% at the minimum focus distance of 0.35 m. Surprisingly, the impact is not as bad as one might think due to its very straightforward barrel shape. Further, when the lens is used with a digital camera as I did for this Tale, the distortion can be greatly reduced with post-processing.

Next let's take a look at aberration at the mid-range 45 mm focal length with focus at infinity. Spherical aberration is slightly over-corrected. This is because I gave priority to enhancing sharpness by reducing lens zones that cause spherical aberration. There is almost no curvature of field and very little astigmatism. Distortion is almost completely eliminated, measuring just -0.3% at 45 mm. In addition, coma is more symmetrical so users can expect point images to also be symmetrical. Next let's take a look at variations in aberration at short distances. Just as at the maximum wide-angle position, curvature of field tends to become positive but changes in the curvature of field and astigmatism at this focal length are negligible. Spherical aberration continues to be fully corrected until the minimum focus distance although there are more lens zones that cause spherical aberration at short distances. Therefore, the focus position changes very little and good balance was achieved. Further, coma changes to outer coma and there is hardly any change in distortion.

Finally, let's see how the lens performs at the 60 mm maximum telephoto position. We'll start with focus at infinity. Spherical aberration is minimal and flat. Measuring just +0.57%, distortion is barely visible. Chromatic aberration is well suppressed. There is a slight tendency toward inward coma. This is the result of a technique by which allowing a little inward coma at infinity reduces visible changes in aberrations at short distances. To achieve this coma balance, curvature of field and astigmatism are kept to a slightly positive degree. Now we'll look at variations in aberration at short distances. Just as at the maximum wide-angle position, curvature of field tends to become positive but changes in the curvature of field and astigmatism at this focal length are negligible, as they were at the mid-range focal length. Spherical aberration was minimal and flat, but it bulges at short distances, where there are more lens zones that cause spherical aberration and full correction was applied. Even at short distances, a good balance that maintains sharpness has been achieved. In addition, there is a tendency toward outer coma, but its effects are not visible. Distortion is almost nonexistent at -0.04%.

Next, let's look at point-image intensity distribution and spot diagrams. Again, we'll begin with performance at the wide-angle 30 mm position with focus at infinity. Along the focal plane, point images are well formed and relatively sharp from the center of the frame to the edges. There is some very faint flare around the core, but pleasing normal (Gaussian) distribution is achieved. As expected from the aberration, the flare expands outward as it moves away from the optical axis. What about defocus? With little astigmatism, defocus produces relatively smooth blur at all image heights. This means users can expect more beautiful bokeh, especially in the background.

What do point images look like at the mid-range focal length of 45 mm? Point-image performance is similar to that at the maximum wide-angle position. Point images are also relatively sharp from the center of the frame to the edges at the mid-range focal length. Again, there is some very faint flare around the core but pleasing normal (Gaussian) distribution is achieved. At lower image heights, the flare extends inward but decreases for sharper point images as the image height increases. Even at mid-range focal lengths defocus produces relatively smooth blur at all image heights due to a lack of astigmatism. This means users can expect more beautiful bokeh, especially in the foreground.

Finally, the 60 mm maximum telephoto position. As we might have expected, there is little change in the characteristics of point-image formation. It is worth noting that point images are more sharply rendered than they are at 45 mm and there is less flare. There is a very small amount of flare around the core, and pleasing normal (Gaussian) distribution is still achieved, but apparently the core is sharp with less flare. As with the 45 mm focal length, flare extends inward at lower image heights and takes on a point-symmetric shape as the image height increases. This means users can expect relatively smooth bokeh at all image heights at the maximum telephoto position but even more beautiful bokeh in the foreground.

Now for MTF characteristics. We'll start by checking contrast reproduction at 15 and 40 lines/mm at the wide-angle 30 mm position and maximum aperture with focus at infinity. At 40 lines/mm, 62% of the original contrast is preserved at the center of the frame. Spherical aberration is fully corrected, and because lens zones that cause spherical aberration are relatively small, sufficient contrast is maintained even with 40 lines/mm MTF measurement. Contrast decreases gradually as the image height increases. The focus peak shifts in the negative direction along both the sagittal and meridional image planes following the curvature of field. At a height about 50% of the total image height, the 40 lines/mm MTF value drops to about 31% along the meridional plane and 35% along the sagittal plane. However, as the image height increases, the speed with which contrast drops slows. At a height 70% of the total image height, the 40 lines/mm MTF value is maintained at about 30% along the meridional plane and 40% along the sagittal plane. Now let's look at results for 15 lines/mm. 84% of the original contrast is preserved at the center of the frame. Even off axis, contrast remains consistent to a height of 85% the total image height. It holds at approximately 68% along the sagittal plane and 61% along the meridional plane. Even at the maximum height, contrast does not drop suddenly, but holds at around 40%.

Now for MTF measurements at the mid-range 45 mm focal length. Contrast at the center of the frame is 65% at 40 lines/mm. Spherical aberration is slightly over-corrected, and because lens zones that cause spherical aberration is relatively small, sufficient contrast is maintained even with 40 lines/mm MTF measurement. The drop in contrast is moderate and nearly linear as the image height increases. The image plane is basically flat. At a height about 50% of the total image height, the 40 lines/mm MTF value is about 54% along the meridional plane and 63% along the sagittal plane. At a height 70% of the total image height, the 40 lines/mm MTF value is maintained at about 44% along the meridional plane and 56% along the sagittal plane. It is clear that sufficient contrast is maintained all the way to the edges of the frame. How is performance at 15 lines/mm? Contrast at the center of the frame is about 84%. Even off axis, contrast remains a consistent 70% to a height of 85% the total image height along the sagittal and meridional plane. Contrast does not drop suddenly but holds at around 60%, even at the maximum height.

Finally, let's look at MTF values at the 60 mm maximum telephoto position. At 40 lines/mm, 85% of the original contrast is reproduced at the center of the frame. Thanks to extremely flat, bulge-free spherical aberration, superior contrast is maintained, even with MTF measurement at 40 lines/mm. However, contrast does decrease gradually as the image height increases. The focus peak shifts in the positive direction along both the sagittal and meridional image planes following the curvature of field only at and near the maximum image height. At a height about 50% of the total image height, the 40 lines/mm MTF value drops to about 35% along the meridional plane and 44% along the sagittal plane. However, as the image height increases, the speed with which contrast drops slows to an almost flat curve. At a height 70% of the total image height, the 40 lines/mm MTF value is maintained at about 36% along the meridional plane and increases slightly to 48% along the sagittal plane. Now for 15 lines/mm. 97% of the original contrast is preserved at the center of the frame. Off axis, contrast remains a consistent 40% to a height of 85% the total image height. At the 60 mm maximum telephoto position, images are very sharp and clear in the center of the frame. However, we can assume that contrast is compressed by flare, resulting in soft rendering characterized by thin lines at the edges of the frame.

V. Actual performance

Next let's look at results achieved with some actual images of distant scenes. I used the Nikon Z 7 with an IX-Nikkor 30-60mm f/4-5.6, the rear side of which was modified for use with the camera. I will talk about the modified lens later.

I will explain performance at each aperture setting in detail. Evaluations are subjective, and based on individual preferences. Please keep in mind that my opinions on sample images and evaluations are for reference purposes only.

30 mm focal length (maximum wide-angle position)

f/4 maximum aperture
There is no noticeable flare from the center of the frame to the edges, and contrast is good. Images are sharp and clear for good image quality, especially at the center of the frame.
There is some flare at the extreme edges and corners of the frame, but details are sharply rendered. I like the lack of noticeable image blurring or color fringing.

f/5.6
Stopping down the aperture by one stop further increases sharpness and especially contrast throughout the entire frame. Nearly all flare is eliminated.
Resolution from the center of the frame through the mid ranges was relatively good, but does seem to have increased somewhat.
Stopping down the aperture increases contrast and clarity for excellent image quality.
Issues at the extreme edges and corners of the frame are also resolved. Flare is eliminated.
By the way, I don't think there would be any significant issues if the lens were used with an FX-format camera.

f/8
Image quality throughout the frame increases a little more. Image quality is perfect with no flare. Details are even sharper.
This aperture setting achieves superior image quality throughout the frame. I would recommend this aperture setting for everyday use.
Image quality at this aperture setting is good enough to the extreme edges of the frame for use with an FX-format camera.

f/11
Consistently good image quality is maintained throughout the frame. Image quality seems very slightly better, but there also seems to be some roughness.
I wonder if the effects of diffraction are beginning to show.
While image quality increases at f/5.6, f/8 and f/11, aperture settings of f/8 to f/11 are recommended to achieve the depth of field suited to landscapes.

f/16
While there is more consistency throughout the frame, there is a slight drop in resolution. The effects of diffraction are beginning to show.

f/22 to f/32
There is a clear drop in resolution that is likely the result of diffraction. It is probably better not to stop down the aperture this much.

45 mm focal length (mid-range)

f/4.8 maximum aperture
Just as at the maximum wide-angle position, there is no noticeable flare from the center of the frame to the edges and contrast is good. Details are sharply rendered for good image quality, especially at the center of the frame.
There is some flare at the extreme edges and corners of the frame, but details are sharply rendered. I like the lack of noticeable bleed or colored flare.
It's almost as if the image captured at the maximum wide-angle position was cropped. Even with an FX-format camera, there is a small amount of flare at the extreme edges of the frame, but sharpness and clarity are such that the lens could easily be used.
The image quality is pleasing with no image blurring or color fringing at the edges of the frame.

f/5.6
Stopping down the aperture by one stop further increases sharpness and especially contrast throughout the entire frame.
Resolution from the center of the frame through the mid ranges was relatively high from maximum aperture, but it has become even better.
Stopping down the aperture further increases contrast and clarity for excellent image quality.
Issues with resolution at the extreme edges and corners of the frame are also resolved. Even when used with an FX-format camera, the increase in resolution is such that lens performance is satisfactory despite the flare that remains at the extreme edges of the frame.

f/8
Image quality throughout the frame increases a little more. This aperture setting achieves superior image quality throughout the frame. I would recommend this aperture setting for everyday use.
Further increases in sharpness and detail make the lens even better suited to use with an FX-format camera despite the flare that still remains at the extreme edges of the frame.

f/11
Consistently good image quality is achieved to the extreme edges of the frame, for a sense of even more improvement.
While image quality increases at f/5.6, f/8, and f/11, aperture settings of f/8 to f/11 are recommended to achieve the depth of field suited to landscapes.
The biggest differences occur when using an FX-format camera. When an FX-format camera is used, flare is eliminated at the extreme edges and corners of the frame.
Images are consistently sharp and clear throughout the entire frame. If using the lens with an FX-format camera, the best image quality will be achieved at f/11.

f/16
While there is more consistency throughout the frame, there is a slight drop in resolution. This is the aperture setting at which we begin to see the effects of diffraction but they're not as bad as one might think. It still stands up to use with an FX-format camera.

f/22 to f/32
There is a clear drop in resolution that is likely the result of diffraction. It is probably better not to stop down the aperture this much.

60 mm focal length (maximum telephoto position)

f/5.6 maximum aperture
There is no noticeable flare from the center of the frame to the edges, but contrast is a little low. Resolution is excellent.
Image quality is particularly good at the center of the frame. Images exhibit sharp detail, but have a little low contrast.
There is no noticeable image blurring, but there is a little color flare.
However, the lens seems to stand up to use with an FX-format camera from maximum aperture despite the flare at the extreme edges of the frame.
Image quality is consistent throughout the entire frame.

f/8
Contrast increases noticeably. It seems as if image quality suddenly increased throughout the entire frame. Flare is eliminated at the extreme edges and corners of the frame throughout the DX-format area.
This aperture setting achieves superior image quality throughout the frame. I would recommend this aperture setting for everyday use.
However, when used with an FX-format camera at this aperture setting, some flare remains at the extreme edges of the frame. The noticeable increase in image quality makes up for that.

f/11
Consistently good image quality is achieved to the extreme edges of the frame, for a sense of even more improvement.
While image quality increases at f/5.6, f/8, and f/11, aperture settings of f/8 to f/11 are recommended to achieve the depth of field suited to landscapes.
When an FX-format camera is used, flare at the extreme edges of the frame is eliminated. Image quality is further increased throughout the entire frame. This is the aperture setting I would recommend.

f/16
While there is more consistency throughout the frame, there is a slight drop in resolution. This is the aperture setting at which we begin to see the effects of diffraction but they're not as bad as one might think. It still stands up to use with an FX-format camera.

f/22 to f/32
There is a clear drop in resolution that is likely the result of diffraction. It is probably better not to stop down the aperture this much.

VI. Sample images

Now let's confirm these rendering characteristics with some sample photos.

Portrait and other Picture Controls that apply less sharpening are generally used for sample images captured for use in NIKKOR The Thousand and One Nights tales in order to best judge the characteristics of the lens. Further, no special compensation including sharpening was applied to enhance image sharpness. I concentrated on capturing the sorts of landscape snapshots I assume general users of this lens would capture.

Sample 1 was captured with an FX-format camera at the maximum wide-angle 30 mm focal length and maximum aperture of f/4. The scene is partially backlit, and the shooting distance was almost that at which landscapes are often captured. Image formation within the DX range is sufficiently sharp, but decreases significantly near the edges where the FX range lies and which was not considered with lens design. However, there is sufficient light throughout the frame with none of the usual drawbacks associated with wide-angle focal lengths.

Sample 2 was captured with an FX-format camera at the maximum wide-angle 30 mm focal length and aperture setting of f/5.6. Issues that occurred at the edges of the frame at maximum aperture are corrected by stopping down the aperture to f/5.6. Image quality is improved even in the vicinity of the most extreme edges of the frame. Although this was not expected from a design perspective, image quality at these settings is sufficient even for the FX format. Naturally, the DX range of the image is sufficiently sharp, making this a decent lens for landscape photography.

With Sample 3, the lens was zoomed in just a little to the 35 mm focal length. It was also captured with an FX-format camera and aperture set to f/5.6. Zooming in has an effect similar to cropping. I think you can see how reducing the angle of view to that of the 35 mm focal length achieves sufficient sharpness all the way to the extreme edges of the frame, even with the FX format.

Sample 4 was captured at a mid-range focal length of 42 mm. This image was also captured with an FX-format camera at nearly maximum aperture. Though the lens was never intended for use with a full-frame camera, image formation at the extreme edges of the frame is sharp and clear. When two-group zoom lenses are used, the most stable results are achieved at mid-range focal lengths. This lens exhibits the same tendency, and it is clear that it offers more than sufficient performance.

Sample 5 was captured with an FX-format camera at the maximum telephoto 60 mm focal length and an aperture setting of f/5.6. Even with telephoto shooting, the lens is well suited to an FX-format camera. There are no issues with image quality. Even at maximum aperture, the lens exhibits adequate potential to the extreme edges of the frame.

Sample 6 was also captured with an FX-format camera at the maximum telephoto 60 mm focal length and an aperture setting of f/5.6. For this image I included small objects, such as grass, so you could better judge the lens' resolving power. What do you think? I'm sure you'll agree that the small objects are sufficiently sharp. It's a happy accident that the designers didn't expect, but I think you can see that this lens is a good pancake zoom lens for the FX format.

VII. Nikon Station's Mr. Chôjûrô

There used to be a forum on the Internet, which I previously introduced with Tale 19, called "SNIKON" (Nikon Station) that was used for the exchange of information between Nikon customers. The forum was launched in 1995 and sadly terminated in 2006 with the closing of the online service that hosted it. At the time, Nikon Station had a number of rooms, each of which had its own particular theme. Participants referred to each other by unique handles. The service utilized the computer communications that can be considered a precursor to today's social media. At that time, however, the service and forum were very exciting and became a social phenomenon. I began participating in in-person meetings of participants around the year 2000. Many of the relationships I established at that time remain intact today. With this Tale, I would like to introduce Mr. Chôjûrô, one unique friend I made through Nikon Station.

Participants in Nikon Station, which could be considered a social media platform of that time, were from all over Japan. Chôjûrô lives in Osaka. He is loyal and compassionate. Five years older than I, he is very dexterous and skillfully modifies cameras and lenses, making small components by hand. I suspect he has knowledge of, and experience with, mechanical and/or electrical engineering. These days, modifying and repairing EE control units (such as adding a power supply part to an EE control unit that has no power supply) is his forte. Not only do his repairs and modifications work, but the beauty and precision with which his work is finished makes the components look like genuine original products. I, on the other hand, am extremely clumsy. Even if I understand the schematics, I am not good at repairing lenses. Whenever I reassemble a lens, I end up with leftover screws. The difference in the precision and skill of Chôjûrô's work compared to mine is like day and night. In fact, Chôjûrô modified the lens barrel protruding from the mount on the IX-Nikkor 30-60mm f/4-5.6 I used for this Tale so the lens could be used with a standard F mount. Of course, such modification is not recommended, but auto-exposure and autofocus work normally. Exif data is also accurately saved.

One day, out of the blue, a package from Chôjûrô arrived. The inside of the package was very clean and tidy. Initially, I was surprised by the beautiful packaging that expressed his personality. When I removed the packing material, I found a lens and a letter. I e-mailed him in a rush of excitement. He said he'd modified two lenses, and was giving me one of them. His gift to me was an IX-Nikkor 30-60mm f/4-5.6 (shown at right) he had beautifully modified to remove the large protrusion on the mount. It was amazing! It seemed the electronic board was positioned where the protrusion had been with no gaps at all. He didn't remove it, but skillfully moved it back. Obviously, without affecting the path light would take through the lens. The moment I saw it, the face of the lens barrel designer passed through my mind. You can do it! With that thought in my mind, I looked at the lens with a wry smile. The work was beautiful and not at all that of an amateur. I do not know what Chôjûrô's actual job is, but I imagine he must be familiar with machining. Then I received another e-mail from Chôjûrô. He wondered why the lens could be used with a full-frame camera. The beam of light used by a full-frame camera illuminates the entire wide-angle 30 mm to telephoto 60 mm range of focal lengths with no vignetting. However, the range in which aberration is well corrected is limited to the DX-format range. Performance at the edges of the frame, especially with regard to curvature of field near the outermost edges, deteriorates with an FX-format angle of view. There is, however, still plenty of light. Why do you think this is? Why did the design include such an unnecessary feature? It's because the original 28-60mm zoom lens was reduced to a 30-60mm zoom lens. This is what made the full-frame pancake lens possible. The FX-format pancake zoom lens was the result of mere chance. Ironic, isn't it? IX-Nikkor lenses were short-lived and doomed from the start. They can, however, still be used for fun. I'm quite certain that is what Chôjûrô wanted me to know. I hope to continue to enjoy photography and its associated equipment with Chôjûrô and other previous members of Nikon Station for years to come.