NIKKOR - The thousand and one nights No.73 | NIKKOR - The thousand and one nights (2023)

Nikon's first native teleconverters, strong allies for students
O Teleconverter Nikon TC-1 2x

Tale 73 takes us back to the days before automatic indexing of maximum opening (AI). It's 1976 and Nikon and NIKKOR are making great strides towards AI. At that time, the long-awaited teleconverter was released. Since the AI ​​capability could not be waited for, an aperture that was not coupled to the camera's light meter was used. The teleconverter had a nice aperture scale and used a high-end mechanism. The TC-1 was released at a time when there was a great demand for a native Nikon teleconverter.

What kind of lens was the TC-1 teleconverter left over from that era? And how did you get from development to final release? This story unveils the mysteries of the mysterious TC-1 teleconverter.

by Haruo Sato

I. The Convenience of Teleconverters

Historically, teleconverters have been the strong allies of high school students, especially elementary and high school students. However, major camera manufacturers have traditionally not included teleconverters in their lens lines. Teleconverters were primarily made and sold by specialized third-party manufacturers who marketed them as inexpensive and practical tools. Even I was very dependent on them when I was in high school. They were the dream tools that effectively turned regular lenses into telephoto lenses. 50mm became 100mm, 200mm became 400mm and so on. They also doubled the size of the main subject for close-ups. They were also incredibly fun toys, selling for about 7,000 to 8,000 yen at the time. Unfortunately, these dream tools also had their downsides. They caused a significant drop in optical performance. The teleconverters I used could not be used wide open. In order to produce images that withstand any kind of magnification, the aperture had to be reduced by two or three stops. Even as a child I understood that nothing in the world is good. I'm sure everyone my age has had the same experience. At the height of the teleconverter boom, there were many options to choose from, including 2x, 3x, and 2-3x zoom teleconverters (varifocal lenses), as well as innovative products whose optics can be removed and used up close. play. Unfortunately none of them were suitable for real pictures. I think that's probably what motivated camera manufacturers to create their own high-performance teleconverters.

II. Why was the Nikon TC-1 teleconverter developed?

The TC-1 teleconverter was developed in a hurry. Why couldn't developers wait for the big innovation that would come with the introduction of AI the following year? There was a reason.

The TC-1 was developed in response to demand from sports photographers and the press. They told Nikon that the fact that they could only use limited equipment at certain events was a big problem. Social trends quickly reduced the space reserved for photographers, which in turn severely limited the amount and type of gear they could bring to various events. Telephoto lenses were limited in number and length. Photographers had great difficulty deciding what to bring to events and what not. They suggested that this dilemma could be greatly alleviated through the use of teleconverters. However, the teleconverters available at the time did not offer the optical performance these professional photographers needed. Newspaper and sports photographers have longed for a teleconverter that doesn't increase aberrations and offers the same optical performance as a double focal length prime lens. Those were indeed lofty goals. Nikon's answer to these needs was the TC-1 and TC-2 teleconverters. Specially design two teleconverters with a focal length of 200mm as the dividing point. The development team's idea hit the mark, and the two TC-1 and TC-2, which were developed at breakneck speed, were well received by sports photographers and the press.

3. Development and construction history.

According to the records of a certain researcher, the TC-1 would have appeared in March 1976. However, based on my research, it's unclear when exactly it was launched, and whether the TC-1 was only supplied to printers and other professional photographers, or the general public. A total of around 5,000 units were produced. Its successor, the TC-200, was launched in May 1977, so the TC-1 was built and sold for about a year. That's an extremely short lifespan for a lens, and it's shrouded in mystery.

Let's take a look at the development history. It is unclear when optics design began, but it was completed in November 1975. The optics were designed by Soichi Nakamura in the 1st Optics Division, Optical Design Department, a character who appears frequently in the NIKKOR short stories “The Thousand and One Nights.” Production testing began in December 1975, one of the busiest times of the year, and quickly went into mass production. The Optical Design Report was not produced until sometime after the TC-1 went on sale in March 1976. I believe this rapid development was only possible because the TC-1's barrel had very few moving parts and the optics were stationary. One can only surmise that with so little preparation time for sale or promotion, the TC-1 was only made available to, or sold to, the press and other professional photographers as prime customers. In March 1977, Nikon made the epic transition from a high-end conventional mounting system to its new AI system. The TC-1 teleconverter was quickly modified to support AI and released in May 1977 as the TC-200 with the same optics as the TC-1. The TC-200 was soon followed by the TC-201. With the release of the TC-200, the TC-1 served its purpose.

4. Construction and properties of the lens

(Video) NIKKOR | The Thousand and One Nights | Night Life

Now let's take a look at a cross section of the TC-1 teleconverter (Figure 1). Please forgive me if the following is too technical.

In general, the teleconverter (rear) is a concave lens (negative refractive power). Hence it has a negative focal length. A convex main lens on the front followed by a concave lens results in a telephoto lens with a telephoto-like design. How to build this teleconverter? Figure 1 shows us that it has a two-group structure with a first concave group and a second convex group. It is characterized by a structure similar to that of a retrofocal lens. Why did the designer choose this structure? Part of the reason for this was to maintain a flat focal plane and to ensure a positive Petzval sum. Many older teleconverters had field curvature and insufficient compensation for astigmatism due to Petzval sum degradation. While they performed well in the middle of the frame, performance always seemed to drop off at the edges of the frame. Nakamura devised a way to correct for spherical aberration while maintaining a positive Petzval sum. The two-group concavo-convex structure was the way to go. If we direct our attention to the convex posterior group, we will see that there are more concave elements than convex elements, although the group as a whole is convex. Thereby, the convex element of the lens can be provided with great power. Glass with a very low refractive index was used for this convex lens element. This structure results in a high Petzval sum as well as good compensation for spherical aberrations and coma.

Now look at how aberration compensation works. While a simple assessment is difficult, we can compare the aberration between images captured with a 50mm f/2 prime lens and those captured with the same 50mm f/2 prime lens with recorded on the TC-1. When using the Teleconverter TC-1, the chromatic aberration is doubled. Since the TC-1 was a 2x teleconverter, this level of compensation is very good. Although there is little difference from spherical aberration, a higher order negative aberration may be produced due to the strong convex element used in the second group of the TC-1 teleconverter. This tends to result in a nice background bokeh effect. There is also little difference in terms of field curvature, and unlike older teleconverters, this field curvature is slightly negative. Petzval's value is halved when using TC.1, but still maintains a sufficiently positive value. At a medium viewing angle, the coma tends towards the outer coma, but this hardly affects the imaging performance. The distortion hardly changes, although there is some change in the positive direction.

Now let's look at the MTF values. If we look at the contrast in 10 and 30 lines/mm charts, we can see that the TC-1 is struggling to maintain the MTF values ​​achieved when only the 50mm f/2 lens is used. In the middle of the frame there is hardly any difference. MTF values ​​in the meridian plane exhibit a smooth curve, indicating an increase in field curvature. When I say it moves movies back slightly to the background once at the MTF peak in the middle of the frame, and then moves movies to the foreground at the edges of the frame, it might be easy to understand. This tendency is the only weakness of the TC-1.

V. The Secret of the Nikon TC-1 Teleconverter

I was introduced to the TC-1 around 1986, shortly after I started working for Nippon Kogaku K.K. to work. (now Nikon's). I found the unusual teleconverter while browsing a gear store. It made sense. How interesting! I have used TC-1 which I discovered as an opportunity to learn from someone with far more knowledge and experience than me. This is how I got to know the rear converter optics. This is about the end of my relationship with TC-1 for a long time. However, on a midnight online spree, I found a TC-1 teleconverter for sale. I love the beautifully engraved Aperture fingerboard and that gorgeous tip, so I bought it without a second thought. The TC-1 I bought looked like new, but something was wrong with the docking mechanism. Pairing was only possible when the lens aperture was set to f/2 or slower. Did not lock when lens aperture was set above f/2. While there appears to be a slot for the end coupler, it wouldn't rotate as much. I examined the teleconverter thoroughly and did a lot of research, assuming I had been tricked into buying a piece of junk. It turns out that the teleconverter is in perfect condition. Cannot be used with lenses with a maximum aperture greater than f/2 as light passing through these lenses will be blocked. I analyzed the project values ​​and was completely satisfied. The reason for all my problems is that Nakamura designed the teleconverter based on the assumption that it would be used with a 50mm f/2 lens. Even if it could be attached to an f/1.4 lens, the TC-1's front lens group would narrow the aperture down to f/2. What if the TC-1 was designed to be used with f/1.4 or f/1.2 lenses? I can't help but wonder, so I gave it a try. However, I was not able to get satisfactory optical performance. It looks like setting an upper limit of f/2 was absolutely correct. In the end, I found there was nothing wrong with the TC-1 teleconverter I bought.

MOUNTAINS. Actual performance and sample images

Next, let's look at the results obtained with some real-world images of distant scenes. I used the AI ​​Nikkor 50mm f/1.8 developed by Nakamura, scaled down to f/2. When using the TC-1, the lens is effectively a 100mm f/4 lens. I also tried using a Nikkor Auto 105mm f/2.5 (new). I thoroughly evaluated the TC-1 by comparing images taken with the above two lenses with and without the TC-1. The camera I chose was the Nikon Z 6 with the FTZ mount adapter. Although the FTZ mount adapter officially supports AI lenses, I chose this configuration as a special case, confirmed by project drawing and actual use.

Performance details are listed for each aperture setting. Ratings are subjective and based on individual preferences. Please note that my opinions on the sample images and reviews below are for reference purposes only.

AI 50 mm f/1.8 com TC-1

f/4 (main lens set to f/2)

The reflection blurs the whole image slightly, but the resolution is good from the center to the middle and outer part of the frame, giving it a three-dimensional look. There is some distortion at the outer edges of the frame, likely caused by astigmatism. There's also a bit of flare when this lens is used alone at or near maximum aperture, so the results achieved with the TC-1 aren't bad.

f/5.6 (main lens set to f/2.8)

Reducing the aperture to f/5.6 reduces flare and increases sharpness and contrast, especially in the center of the frame. However, the slight distortion at the very edges of the frame has yet to be addressed. The lack of flashes can even serve to make it more noticeable.

f/8-11 (main lens set to f/4-5.6)

Detail and sharpness are further enhanced at f/8. Distortions at the edges of the frame are also eliminated. F/8 is the boundary that separates images that can be used to the edge in terms of image quality from those that cannot. Excellent image quality is achieved at f/11, maintaining sharpness in most of the image except for the very edges. The middle and middle bands of the frame show the most detail and sharpness at f/11.

f/16-22 (main lens set to f/8-11)

Consistent image quality is achieved over the entire frame. However, there is a loss of resolution, possibly due to diffraction.

Nikkor Auto 105 mm f/2.5 (nova) mit TC-1

f/5 (main lens set to f/2.5)

There is minimal glare. The resolution is good for three-dimensional optics. The most obvious problem is increased axial chromatic aberration. Performance at the edges of the frame is relatively good. The good resolution is maintained up to the very edges of the frame. This lens and the TC-1 seem to work really well together.

f/8 (main lens set to f/4)

Reducing the aperture to f/8 reduces flare and increases sharpness and contrast. The increased depth also serves to eliminate the effects of axial chromatic aberration in the image plane.

f/11 (main lens set to f/5.6)

Detail and sharpness are further enhanced at f/11. Good image quality is obtained over most of the frame except for the extreme edges. I believe this is the ideal aperture setting for this lens and teleconverter combination.

f/16-32 (main lens set to f/8-22)

An even smoother reproduction is achieved over the entire frame, although the resolution drops. Diffraction effects are visible and resolution suffers somewhat.

After testing the TC-1 with two different lenses, I found that good results can be achieved with both when using an aperture setting of f/8 to f/11 (the aperture stops at one or two stops).

Now let's validate these rendering abilities with some sample shots.
These images have not been edited or enhanced so you can judge the capabilities of this lens for yourself. I also used the AI ​​50mm f/1.8 and Auto Nikkor 105mm f/2.5 (new) with the TC-1 on a Z 6 mirrorless camera to capture these sample images. Most of the sample images are portraits because I think that's how most people would use the lens/converter combo. I added backgrounds to the images and slightly adjusted the shooting distance to better show the 3D rendering properties.

Sample 1 was shot with the AI ​​50mm f/1.8 and TC-1 at an aperture setting of f/4 (main lens set to f/2). Looking at the wood panel pattern, the model's face and hair, you can see that the image has sufficient sharpness. There is also no significant drop in sharpness in the central and peripheral parts of the frame. Consistent rendering is maintained across the entire frame. Unfortunately, the background bokeh is quite difficult. However, the overall impression is good, with very little color gradient along the plane of focus.

Sample 2 was also shot with the AI ​​50mm f/1.8 and TC-1 like Sample 1. The image has satisfactory sharpness, but the bokeh is not very appealing.

Sample 3 was also shot with the AI ​​50mm f/1.8 combination. I tried changing the distance to the ground a bit. It didn't do much to improve the bokeh appearance. There doesn't seem to be any other way to improve bokeh other than narrowing the aperture a bit. The teleconverter reflects the performance level of the master lens well, but it doesn't look like bokeh has been incorporated into the TC-1's design.

For Show 4 I switched to the Auto Nikkor 105mm f/2.5 (new). When used with the TC-1, the focal length is 210mm and the maximum aperture is f/5. I recorded sample 4 in these settings. Sharpness and consistency increase with the narrower angle of view of the main lens. This combination also makes it clear that any problems with the TC-1 are minimized. The bokeh effect is nicer too, although increasing axial chromatic aberration leads to more color fringing in out-of-focus areas.

I also used the Auto-Nikkor 105mm f/2.5 (new) for Probe 5. When used with the TC-1, the focal length is 210mm and the maximum aperture is f/5. This picture was also taken with these settings. Distance to background and border have been changed. There is no break in the bokeh.

Sample 6 was photographed at close range. Teleconverters have the effect of enlarging close-up shots without changing the shooting distance. One of the biggest advantages is the ease with which macro photography becomes possible. I took this picture with the Auto-Nikkor 105mm f/2.5 (new) at the shortest focusing distance (R=1m). Because the subject is enlarged without changing the working distance, the TC-1 is a simple and practical tool for macro photography. The TC-1 works well with this lens and gives satisfactory results even at close range.

VIII. Zoom Teleconverter and AF Teleconverter

There are many different types of teleconverters. Many unique teleconverters have also been released, opening up opportunities for further development. Two particularly convenient dream converters are the tele zoom converter and the tele auto focus (AF) converter.

In 1964, Sankyo Kohki released the Komura Telemore-Zoom 2x ←→ 3x zoom teleconverter. Introduced for the hobbyist market, this zoom teleconverter easily allowed 2-3x zoom with fixed focal length lenses. The teleconverter has been divided into two lens groups. By bringing these groups into the main lens at different speeds, the magnification was increased from 2x to 3x. This innovative converter was actually a varifocal lens that increased magnification from 2x to 3x. I was a sophomore in high school when this converter came out. These specs seemed like magic to me. When used with a 50mm lens, it becomes a 100-150mm zoom lens. I remember forgetting the time looking at this little marvel displayed in a camera shop window. At the same time, even as a child I had a strange, inexplicable feeling, as if a fox had put a spell on me. I thought about it for a long time, but I didn't buy the Komura Zoom teleconverter. I ended up buying a regular 2x teleconverter. But thoughts of that magical zoom teleconverter stayed in my subconscious. Was it really a magical tool? I hadn't even tried. There wasn't as much fuss about it as you might expect. It took me 40 years to find this product again. I bought it and tried it on right away. Unfortunately, it wasn't as magical as he thought it would be. I felt like the knot in my stomach was finally gone.

How do you think a zoom teleconverter is used to zoom? Magnification is adjusted by changing the distance between the convex main lens and the concave teleconverter. The physical problem of magnification adjustment affects not only zooming but also focusing. That's the way it is. It can also be used for focusing. Every photographer's dream tool has finally been achieved. In 1983, the TC-16 AF teleconverter was born. Designed for use with the F3AF, this dream tool turns manual lenses into AF lenses. The TC-16 increased the focal length of the lens by 1.6 times. It was an innovative teleconverter that performed autofocus by moving the part of the teleconverter with the built-in motor. Lens group moved to adjust magnification. The TC-16 was a high-performance teleconverter with a 1980s optical design large enough for practical use. Manual AI Nikkor lenses converted to AF lenses. It really was a magical tool. The TC-16 has been replaced by the TC-16A AF Teleconverter for the F-501 (N2020) and F4.

The installation of converter lenses offers great added value. There are still many options for this type of product. Soft Focus and Blur Image Control (DC), used to control bokeh, are just two of them. We'll talk more about converters that hide dream mechanics next time.