Developer Interviews

The f/2.8L and f/4L Zoom Lens Series:
Ever-evolving lenses that meet the expectations of professional users

Developer profiles

Product planning Image Communication Business Operations
ICB Optical Business Management Div.
Manager
Kengo Ietsuka

Ietsuka is in charge of EF lens series product planning. He is working on productization and performance improvement of EF lenses, including the f/2.8L and f/4L zoom lenses.

Optics design Image Communication Business Operations
ICB Optical Products Development Center
Senior Engineer
Hiroshi Endo

Endo has been involved in the optical design of the EOS system from its start. Since joining Canon, he has been working on development and design of the large diameter aspherical lenses that are a key technology of the large aperture L zoom series.

Mechanics design Image Communication Business Operations
ICB Optical Products Development Center
Manager
Shigeki Sato

Sato has been in charge of EF lens mechanical design since he began working at Canon. His work has contributed significantly to technological innovation and reliability improvements since the rapid acceleration of digitization beginning in 2000.

Electronics design Image Communication Business Operations
ICB Optical Products Development Center
Lead Engineer
Koji Okada

Okada is mainly in charge of IS unit control. Currently he is in charge of systems in matching departments that communicate between the camera and lens, and is working on interoperability between EOS and EF lenses.

Lens processing Image Communication Business Operations
Utsunomiya Plant
Senior Engineer
Hisakazu Nakamitsu

Nakamitsu is promoting efforts to ensure the stable supply of high-quality professional lenses by improving the efficiency of the manufacturing department overall and following up on quality.

Production technology Image Communication Business Operations
Utsunomiya Plant
Assistant Manager
Kenichi Okushima

Okushima is in charge of technical support for mass production. This support contributes to higher precision in ground aspherical lenses and to the automation of high-precision spherical lens processing, and advances the study of new technologies in collaboration with development.

Concepts by lens series

Canon's flagship zoom lenses bring together
state-of-the-art technology and expertise

f/2.8L

Zoom Lens Series

This lens series features a wide range of expression, thanks to large aperture f/2.8 brightness and dramatic blurring. Exquisite optical design, tradition-backed advanced optical theory, and ultra-precision processing technology achieve outstanding rendering performance and excellent operability approaching those of single focal length lenses. These flagship zoom lenses for professionals further incorporate environmental resistance and toughness.

  • EF16-35mm f/2.8L III USM
  • EF24-70mm f/2.8L II USM
  • EF70-200mm f/2.8L USM
  • EF70-200mm f/2.8L IS III USM NEW

High performance zoom lenses that combine
high optical performance and mobility

f/4L

Zoom Lens Series

This compact series offers compelling mobility and affordable prices while maintaining excellent rendering performance. These lenses are designed with portability and ease of handling in mind, envisioning landscape photography and other situations in which photographers want to be lightly equipped. In addition to excellent optical performance and compact size, they offer a zoom range and IS-equipped models not available in the f/2.8L zoom series.

  • EF16-35mm f/4L IS USM
  • EF17-40mm f/4L USM
  • EF24-70mm f/4L IS USM
  • EF24-105mm f/4L IS II USM
  • EF70-200mm f/4L USM
  • EF70-200mm f/4L IS II USM NEW

Chapter 1 The birth of EOS and development of the large aperture L zoom lens group

“It was their dream to create visionary zoom lenses with a large aperture and high image quality for professionals.”

When did the large aperture zoom lens development originate?

Product planning

The first three professional large aperture zoom lenses appeared in the EF lens series in 1989, when the EF 20-35mm f/2.8L, EF 28-80mm f/2.8-4L USM, and EF 80-200mm f/2.8L were released at the same time as Canon’s premium AF SLR camera, the EOS-1. This was the first time that we had three professional zoom lenses with a maximum aperture of f/2.8 in a Canon lens system. The lens designers at the time had a dream of creating visionary zoom lenses with a large aperture and high image quality for professionals using the EF mount. This was a time when many professionals seeking image quality and brightness still used prime lenses. The FD 35-70mm f/2.8-3.5 S.S.C. was very popular upon its release in 1973, and we received a lot of feedback calling for more professional zoom lenses with a bright aperture and high image quality. Technology advanced, and when the three lenses of the EF lens series were released, professionals who had been cool toward zoom lenses also began using zoom lenses that nearly matched single focal length lenses in brightness and image quality.

This may not sound like a big deal now that f/2.8 zoom lenses are being released by every manufacturer, but at the time, no one thought that a zoom lens series starting from f/2.8 would be released in wide-angle, standard, and telephoto models. Without the new ideas of designers who wanted to take on difficult and new challenges as they entered a new era, the large aperture L zoom series might not have gained such strong support from users and become what it is now.

Image Communication Business Operations
ICB Optical Business Management Div.
Manager
Kengo Ietsuka
Product planning

“We aimed to build an AF system that would satisfy professionals with USM-equipped zoom lenses offering a f/2.8 maximum aperture throughout the zoom range.”

Can you tell us about the features of the initial f/2.8 L zoom series?

Product planning

The EF17-35mm f/2.8L USM, EF28-70mm f/2.8L USM, and EF70-200mm f/2.8L USM, which were released as successors to the three large aperture zoom lenses released in 1989, achieve f/2.8 throughout the zoom range. This eliminates fluctuations in aperture value due to zoom position when close to maximum aperture, improving convenience of on-location shooting for a three-lens system and employing an Ultrasonic Motor (USM) in all three lenses makes AF shooting faster and more comfortable. In addition, the telephoto lenses in this line began supporting 1.4x and 2x extenders with the EF70-200mm f/2.8L USM.

Mechanics design

At a time when moving the focus lens with a motor in the body was typical, Canon adopted a proprietary method using a drive system inside the lens. The drive system can be placed at the optimum position for the lens, achieving fast, accurate, quiet AF. The ring-type USM developed at that time was given improvements in shape and control matched to the lens, and performance was further improved.

Product planning

The first product equipped with USM was the super telephoto lens EF300mm f/2.8L USM released in 1987, the year of the EOS system’s birth. It was acclaimed for its ability to focus with high precision by moving the large diameter focus lens quickly and quietly despite a shallow 300mm depth of field. This USM technology was implemented in the f/2.8L zoom series, creating an AF zoom lens system that would satisfy professionals.

Image Communication Business Operations
ICB Optical Products Development Center
Manager
Shigeki Sato
Mechanics design

  • 1973

    A forerunner of large aperture zoom lenses for professionals
    FD 35-70mm f/2.8-3.5 S.S.C.

    As a forerunner of the short zoom lenses that followed, this premier lens left its mark in the history of modern optics.

  • 1987

    Birth of EOS

    The EOS 650 and 620 were released in 1987, the 50th anniversary of Canon's founding. A new fully electronic EF mount system was adopted.

  • 1989

    Pioneer of the f/2.8L zoom lens

    A three-lens series of large aperture zooms released at the same time as the first EOS-1, this is the forerunner of the f/2.8L zoom series that continues to the present. It made the high image quality of the L lenses available to professionals.
    ・EF20-35mm f/2.8L
    ・EF28-80mm f/2.8-4L USM
    ・EF80-200mm f/2.8L

  • 1987

    World’s first practical use of USM

    Canon was the first in the world to successfully implement USM as a lens drive motor. A motor driven by the vibration energy of ultrasonic waves, USM was a nearly ideal lens drive motor in terms of low power consumption, excellent starting and stopping responsiveness, and high controllability, as well as extremely quiet operation.

    World's first super telephoto L lens equipped with USM:
    the EF300mm f/2.8L USM

    With high optical performance and the adoption of the inner focus system and ring-type USM, this is one of the large aperture super telephoto lenses that achieved EOS’ concept of high-speed comfortable autofocus, earning high praise from professional photographers worldwide.

Chapter 2 Accelerated digitization and improved reliability

“Entering the digital era, more users began to appreciate the value of the L lenses.”

Can you tell us some stories from the arrival of the digital era?

Product planning

A big change that happened in the transition from the film era to the digital was an increase in opportunities to print and use photos in large sizes. As a result, developers are required to design lenses with even higher optical performance than before.

Optics design

From an optical design perspective, challenges when designing a zoom lens with a constant aperture value include correcting for spherical aberration on the telephoto end, curvature of field on the wide angle end, and chromatic aberration from the wide angle end to the telephoto end. It is important to appropriately select glass material and aspherical lenses. Simulation software was not as advanced then, so development was very difficult. We made prototypes and tested repeatedly, aiming for the ultimate performance balance worthy of a flagship.

Image Communication Business Operations
ICB Optical Products Development Center
Senior Engineer
Hiroshi Endo
Optics design

Mechanics design

As camera resolution had increased, higher focusing accuracy was required. In response, we revised the entire focus drive. To suppress performance deterioration, we selected an optimal optical adjustment method for each product and made adjustments to each. We also advanced adjustment methods and improved accuracy so that tilting and parallel eccentricity adjustment for each lens group can be performed digitally.

Product planning

The digitalization of SLR cameras led to our further enhancing the optical performance of the L lenses.

Implementing the innovative “zoom linked inner focusing mechanism”.

What was the breakthrough that achieved a standard zoom with a wide angle end of 24mm?

Mechanics design

A wide angle of 24mm on a standard zoom lens was achieved by implementing a zoom linked inner focus mechanism. Conventionally, the focusing method of zoom lenses faced restrictions in optical design, as the amount of focus feed from infinity to close range had to be constant over the range from wide angle to telephoto due to mechanical structure limitations. The zoom linked inner focus mechanism is an innovative focus mechanism that frees the optical design from these restrictions.

Optics design

This innovative focusing mechanism made it possible to use a rear focus or an inner focus system instead of the conventional system that moves the frontmost lens elements. The mechanism allowed us to widen the focal range on the wide angle end while maintaining the overall size. This mechanism is used in the EF24-105mm f/4L IS USM that came out later, and contributes greatly to achieving a high-magnification zoom with a wide angle starting at 24mm.

Electronics design

The mechanism is also used in the successive EF70-200mm f/2.8L series, contributing to more compact telephoto lenses. The focusing lens can be miniaturized, enabling high-speed AF drive.

The first high-zoom lens to use a zoom linked inner focusing mechanism
EF35-135mm f/4-5.6 USM

In 1990, this was the first high-zoom lens from Canon to use the inner focusing method that focuses with the second lens group behind the aperture. By establishing the technology of inner focusing and rear focusing in a zoom lens, it became a standard lens that contributed greatly to the development of multi-group zoom lenses in subsequent EF lenses.

EF28-70mm f/2.8L USM lens cross-section

EF24-70mm f/2.8L USM lens cross-section

“Dramatically improving durability and toughness also increased professionals’ satisfaction.”

Can you tell us about durability improvement from the mid 2000s?

Product planning

One thing that has changed significantly in the digital era is the number of shots taken. The number of shots taken by newspapers and members of the media in particular has increased dramatically, calling for more demanding levels of durability and toughness. Although there are few problems in normal usage, intense impacts are inevitable in press photography, where cameras and lenses are used in extremely harsh environments. Since our aim was to create the No. 1 system in the professional world, we revised the mechanical structure from the ground up and worked on improving durability and toughness.

Mechanics design

The frequently rotated zoom ring is mechanically linked with the internal structure. In the digital era, it is necessary to balance comfortable operability and reliability. Since the mid 2000s, we have used bearings in the linkage section and improved the smoothness of its operation. However, the more complex the interior structure, the further removed it is from comfortable operation. So, we conducted reviews with operability in mind from the optical design stage, and engaged in trial and error on a daily basis. Regarding the dust-proof and drip-proof configuration, simply increasing the level of sealing alone makes operation slow. It was necessary to rethink the flow of air as well as waterproofing, without affecting the appearance.

Product planning

Improving durability made professionals even more satisfied. The invisible specification that a product work properly on location, where reshooting is not an option, is the real specification that professionals demand.

Mechanics design

70-200mm telephoto lenses are often used for sports photography, and troubles that prevent the capture of an instant are unacceptable. Beginning with the EF70-200mm f/2.8L IS II USM released in 2010, we have dramatically improved the durability and toughness of our products.

Image Communication Business Operations
Utsunomiya Plant
Assistant Manager
Kenichi Okushima
Production technology

“Canon's strength is combining high precision with technology for mass production.”

Can you tell us about the progress of aspherical technology for wide angle lenses?

Optics design

How to correct peripheral image quality and lateral chromatic aberration after digitizing is a major issue. Aspherical lens technology is particularly indispensable. Canon has numerous aspherical lens designing and manufacturing technologies such as ground aspherical surface, replica, and glass-molded (GMo), each of which is used appropriately at the right place. The EF 16-35mm f/2.8L III USM succeeded in making both surfaces of a large diameter lens aspherical, and further reduced aberration.

Production technology

Canon's strength lies in the ability to mass-produce large diameter glass molded aspherical lenses, for which high precision is particularly required. The EF 16-35mm f/2.8L III USM uses an extremely large aspherical lens with a 62.5mm diameter. In order to mass-produce this, we took polishing technology and measurement technology for semiconductor exposure equipment, which requires much higher precision than camera lenses, and applied it to lenses for consumers. We are working to further improve the accuracy of shapes in mold performance. Application of this technology to grinding aspherical surfaces achieves required accuracy about 2.5 times that used in conventional lenses.

Aspherical lenses

High precision GMo aspherical lens molds

Can you tell us about the telephoto lens optics?

Product planning

Since chromatic aberration is a problem with telephoto lenses in particular, we use low-dispersion glass such as UD lenses and correct the aberration. We have used fluorite from the EF70-200mm f/2.8L IS II USM, with good reviews from users. With the EF70-200mm f/2.8L IS III USM, we used the latest coating technology ASC in response to requests to reduce flaring, and have increased the product's level of perfection.

Optics design

Although it is not particularly mentioned in the catalog, we use lens materials with high refractive index to suppress chromatic aberration, curvature of field, and peripheral aberration. We have used various types of glass in recent years. At first glance, there are no visible significant changes to telephoto lens optics, but from the viewpoint of the optical designer, it is now possible to use glass that could once have only been imagined. The range of lens design is expanding more and more.

UD lenses

Lens processing

UD lenses are delicate and very difficult to handle. As a result of long research at Canon, about 10 years ago we established automation technology capable of mass-producing UD lenses, and can now supply these with stable quality. In addition, as high precision machining is now possible, the above-mentioned high-index glass can be used.

“We standardize the work of the artisans, and are working to provide a stable supply of high quality lenses.”

What changes have been made at the manufacturing plants due to digitization?

Lens processing

As market demand increased and mass production became necessary in the digital era, the demand for high precision glass elements increased from small lots to several hundred per day. In response, wherever possible we began to standardize (digitize) work that relied on artisan skills. At the same time, we promoted standardization of tools, and actively adopted new processing machines and evaluation equipment. Through these efforts, we successfully mass-produced lens surfaces with very high precision and consistent quality.

Image Communication Business Operations
Utsunomiya Plant
Senior Engineer
Hisakazu Nakamitsu
Lens processing

At the Utsunomiya plant, we succeeded in automating almost all processing steps for high quality and consistent supply. However, problems with the shape and precision of lenses make some things difficult to automate, so we utilize the skills of expert workers in the polishing process for specific parts, and work on transferring these skills.

“Production technology and design work together to create the best relationship by which people interact with information.”

How are the lenses designed and moved to the production line?

Optics design

In lens design, we use Canon's proprietary optical simulation software to design lenses that meet new specifications. We carry out simulations of strength and impact with various materials before trial production, and confirm effects on optical performance. For these simulation technologies, we use computers with outstanding processing power.

Product planning

With simulation technology, it is possible to investigate factors such as how flaring or ghosting varies with zoom position, focal position, and aperture value. This enables designs that takes performance to the limit, toward which the plant works to respond with the necessary precision.

Production technology

Members from the design team and engineering team hold frequent meetings from the early stages of product planning. In these meetings, we discuss what new technologies are needed for a particular product, potential technical challenges, the difficulty of processing and assembling the elements, and the possibilities for automation and through these discussions, we make preparations for mass production.

Product planning

This close cooperation is possible because the design department and the plant are adjacent to each other. This system was adopted in 2000.

Laboratories and plants are closely linked

Optical technology laboratory

Utsunomiya Plant

Chapter 3 Birth of the f/4L zoom series

“We wanted to create a compact and mobile system that inherits the high image quality of the f/2.8L zoom.”

What were the ideas behind development of the f/4L zoom series?

Product planning

The f/2.8L zoom series was extremely well received by professionals, so we thought we would like to make a more compact f/4L zoom series while maintaining the same image quality. We positioned this series as second (backup) lenses for professionals. Put simply, we wanted to create a system that is highly mobile. We were able to reduce the price by decreasing the diameter, and succeeded in developing products for a wider range of high-end users.

Optics design

The f/4L zoom series is a sibling of the f/2.8L zoom series, but its optical performance is not compromised in any way. In fact, a comparison of maximum aperture shows that the two series achieve nearly identical high image quality.

Product planning

The brightness of f/2.8 is appealing and popular, but among professionals, there are people who make a point of choosing f/4. It’s easy to carry, and its mobility means you can quickly take it out and shoot photos at any time. The ease of use of the f/4 zoom lens has also improved recently as the ISO speed of cameras has increased. With the introduction of the f/4L zoom, we were able to create a solid lens system that allows you to select equipment according to shooting objective and taste.

  • 1985

    High image quality and lightweight zoom
    New FD80-200mm f/4L

    Developed as a high-performance lens within the highly acclaimed L lens series. It achieved high performance, small size, and light weight, and hinted at the birth of the EF lens f/4L zoom.

  • 2003

    EF17-40mm f/4L USM
    Released at the same time as the EOS 10D

    With usability as a standard zoom lens for APS-C sized cameras in mind, we made a point of extending the focal length on the telephoto side to provide a zoom range not found in the f/2.8 L zoom series.

  • 2005

    EF24-105mm f/4L IS USM
    Released at the same time as the EOS 5D

    This lens achieved a high-magnification zoom from a 24mm wide angle. It is also equipped with IS not found in the f/2.8L zoom series, for a universal zoom that supports a wider range of shooting scenarios.

“The appeal of the f/4L series is IS that spans wide angle to telephoto.”

Why was the f/4L series able to be equipped with IS?

Mechanics design

The F value of the f/4L series is larger than that of the f/2.8L zoom, so it can be configured with a smaller diameter and without enlarging the lens, even with IS included. It offered us a chance to show our skills in arranging the lens barrel configuration and the IS unit to maintain the high image quality of the f/2.8L.

Electronics design

IS continues to evolve every day, and the latest EF70-200mm f/4L IS II USM achieves IS performance of CIPA standard 5 stops. The shutter speed can be slowed as IS performance increases, but that will require compensation for the low frequency shaking caused by significant shaking of the entire body. To compensate for this, we achieved control that cuts low frequency signals sent from the gyro sensor as little as possible.

Product planning

The f/4 L zoom has four IS lenses that range from wide angle to telephoto. Its appeal is the ability to put together a highly mobile system matched to the shooting objective.

The advantage of the f/4L series is the ability to choose IS for all models, from wide angle to standard and telephoto.

EF16-35mm f/4L IS USM
EF24-70mm f/4L IS USM
EF24-105mm f/4L IS II USM
EF70-200mm f/4L IS II USM

The EF 70-200mm f/4L IS II USM enables handheld night scene shooting. It achieves a CIPA standard image stabilization effect* of 5 stops.

* CIPA standard. With a focal length of 200 mm, using the EOS-1DX Mark II.

IS ON

Focal length: 200mm
ISO 800 1/6sec. f/4

IS OFF

Focal length: 200mm
ISO 800 1/6sec. f/4

“We developed a dedicated EF lens microcomputer chip and succeeded in improving performance and integration.”

Are there any improvements to hidden parts?

Electronics design

From around 2007, we began incorporating dedicated EF lens microcomputer chips. Until then, we used general-purpose microcomputer chips, and controlled USM, IS, and so on through dedicated circuits using external parts. However, general-purpose products did not cover all of the functions that we wanted, and there were problems with the mounting area and performance. Because of this, we started to develop a dedicated microcomputer chip optimized for EF lenses. Our latest microcomputer chip is installed in the EF70-200mm f/4L IS II USM, achieving enhanced arithmetic processing.

Electronics design

The merits of using a dedicated microcomputer chip are high performance and integration. The chip achieves more precise control and contributes to lens miniaturization by reducing the mounting area. We are now striving to evolve further to even higher performance and functionality. Almost all EF lenses released from 2007 have dedicated microcomputer chips for advanced electronic performance.

Image Communication Business Operations
ICB Optical Products Development Center
Lead Engineer
Koji Okada
Electronics design

What does high performance control make possible?

Electronics design

USM low-speed drive and smooth operation of the electromagnetic aperture during video shooting are examples of what is possible. With still image shooting, the demand was for quick focus on the subject, as well as quick aperture action. However, the world of video is the complete opposite, and it was necessary to control both focus and aperture to be slow and smooth.

Mechanics design

Maintaining the operation of focus at low speed with video shooting in mind is difficult for USM, and a new control method, not just an extension of the current one, was necessary. The appearance of the USM remains the same, but how it moves is considerably improved from the initial phase.

Electronics design

The large diameter L zoom is designed to minimize lens operating noise as much as possible, in line with the growing need for video shooting. With the latest EF70-200mm f/4L IS II USM, we have succeeded in suppressing IS drive noise considerably. This is also a result of the dedicated microcomputer chip.

Chapter 4 For improving the satisfaction level of the f/2.8L and f/4L zoom systems

“We are aiming for the ideal lens system for professionals and other high-end users.”

How will the f/2.8L and f/4L zoom series develop in the future?

Product planning

The f/2.8L zoom series and the f/4L zoom series have evolved along with the cameras that professionals use, such as the EOS-1 series and EOS 5 series. We have always pursued lenses that are ideal for professionals. This will continue in the future as well.

Regarding rendering performance, superior operability, durability, and toughness, we have developed only lenses that can satisfy professionals as zoom lenses bearing the designation “L”. To constantly produce better lenses, we face the ongoing challenge of improving design and production technology.

The driving force for lens development-related personnel to continue taking on new challenges is the feeling of wanting to make the best lenses for professionals. We are pursuing thorough performance and quality that will satisfy the professionals of the future.

Even as the environment surrounding images changes, as long as there are professionals pursuing new expression and value in images, we will push the evolution of the professional lens system at the core of the EOS system, in any era.

You can look forward to the future of the professional L zoom system.