Big in Japan: Canon factory
20 amazing facts about Canon lenses that Rod Lawton learned when he took a tour of Canon’s huge Utsunomiya factory near Tokyo, Japan
Discover how Canon builds its lenses in our top-secret tour of its factory in Tokyo
01 Canon Utsunomiya factory facts
Canon’s Utsunomiya lens factory is around 80 miles north of Tokyo, and around 50 minutes by bullet train (Shinkansen). Spotlessly maintained inside and out, this is where Canon makes its L-series lenses using a combination of manual and automated assembly. Workers (and visitors) wear protective clothing and must pass through an ‘air shower’ before entering dust-free environments. Lens manufacture is so precise that the plant’s internal temperature must be regulated to within half a degree centigrade.
02 Lenses are designed with CAD
Lenses are designed using CAD (computer aided design) software that can take into account the physical and optical properties of the glass being used and can predict the final lens’s performance to a high degree of accuracy, and even the ‘sample variation’ between lenses.
03 Why glass is great for lenses
Glass is hard to work with (literally) but it’s still the best material for making lenses because it’s transparent to visible light wavelengths, it’s relatively easy to shape and it’s thermally and chemically stable. But its properties mean you can’t just mould it into the shape you want. Each glass element in a lens must be ground, smoothed and polished to the precise profile required. Typically, this is a six-stage process, including (1) Grinding the glass blank, to remove excess thickness, (2) Smoothing, to reduce cracks, (3) Centring, or grinding the lens edges to make sure it’s optically centred, (4) Rough polishing, to reduce tiny surface cracks still further, (5) Fine polishing, for final shaping, (6) Final polishing, for fine-tuning the surface. Only at this point is the lens ready for inspection.
04 There’s more than one type of glass!
Glass is made of metal oxides and other materials arranged in an irregular pattern. Glass with a regular particle arrangement is called ‘crystal’. Glass that’s somewhere in between is called ‘amorphous’. The metal oxides in glass can include silicon dioxide (silicon is a ‘metalloid’), calcium dioxide (technically, calcium is indeed a metal), lead oxide and titanium dioxide. Every glass has different properties and advantages which the lens designer needs to take into account and exploit.
05 Dispersion, and how to deal with it
All glass produces a prism effect when light passes through it, and optical designers call this ‘dispersion’ or the ‘refractive index’ of the glass. Different glass materials produce different levels of dispersion, and this is measured using the so-called Abbe number. Ernst Abbe (1840-1905), was a prominent German physicist and optical scientist and one-time co-owner of Zeiss, and is considered a pioneer of modern optical science. This dispersion effect causes different wavelengths (colours) of light to come to a focus at different points, causing softening and colour
Canon’s Takumi, Mr Saito, has experience, skills and even senses that the automated machinery can’t match
fringing, so a lot of lens design effort goes into correcting chromatic aberration by using one lens element to counteract the dispersion of another. It’s why expensive ‘low-dispersion’ lens elements are a key selling point for premium lenses.
06 Spherical vs aspherical lenses
Most of the lens elements in a camera lens are ‘spherical’. This means that their shape follows the curvature of a sphere. It might be a very big sphere for a relatively flat lens element, or a small sphere for a strongly curved one, but it’s a sphere nonetheless. Sometimes, though, the optical design calls for a more complex non-spherical lens element. So-called ‘aspherical’ lenses are extremely difficult and expensive to manufacture using traditional grinding and polishing techniques, but Canon has its own glassmoulding machinery at its Utsunomiya plant to manufacture them from molten glass billets. To accomplish this, the mould has to be designed with an extremely high level of precision, and must take into account the exact dimensional changes that will take place as the glass cools down.
07 Mr Saito the Takumi, or ‘craftsman’
As you’d expect, most of the lens processing is done by automated machinery, but at the heart of the process is the Takumi, or expert craftsman who takes the lens design from the drawing board and helps create the physical product. Canon’s Takumi, Mr Saito, has experience, skills and even senses that the automated machinery can’t yet match: “When the lens is touching the diamond plate I know what sound it should be making, so when it’s slightly off I’ll be able to detect with my hearing.” Mr Saito doesn’t just make lenses by hand, he uses his experience to ‘train’ the automated machinery to reproduce the tolerances and accuracy required by the designers. Mr Saito is the only Takumi at the Utsunomiya plant and
he retires in four years, but he is helping to train his eventual replacement (phew!).
08 Canon’s automated lens polishing machines
These have been developed in-house by Canon. They are checked constantly by their operators, of course, but they have also been designed to be self-correcting, automatically checking lenses as they’re produced and making corrections to the process to keep them as close as possible to the design ‘ideal’.
09 The football stadium and a plastic bag
Canon’s highest precision lenses for cameras are for the broadcast 4K/8K industry and have a manufacturing deviation of less than 30nm (1 nanometer is one millionth of a millimetre). That’s hard to imagine, so Canon offers an analogy – imagine a lens large enough to cover the Macaraña Stadium in Rio de Janeiro (built to serve as the flagship venue for the 1950 World Cup, it was meant to become the biggest football stadium in the world) which is roughly 300 metres across. Across its entire surface, this giant lens would demand deviations of less than 0.03mm, which is less than the thickness of a plastic bag!
10 Canon’s ideal EF lens
There’s more to Canon lens design than you might think. Canon cites superior optical performance as one of its aims, of course, but it’s also targeting competitive pricing, accurate auto exposure, size and weight, unique specifications, ergonomics, operability and usability, durability and rigidity, effective image stabilization, autofocus performance and movie shooting capabilities. There’s a lot more in these lenses than just the glass. Canon’s strategy is to introduce new technologies into its L-series lenses and then work out how to pass these down the line to its mid-range products and, where possible, to its entry-level cameras.
11 So what’s the hardest lens to make?
We assumed that the complex internal movements of Canon’s L-series zoom lenses would make them the most difficult to assemble, but in fact it’s Canon’s long L-series telephoto lenses that take the most time to assemble – four times longer than zoom lenses like the L-series 16-35mm f/2.8. They are assembled by specially trained and skilled Canon ‘Meisters’.
12 Every 16-35mm lens is tested
If you’ve ever wondered where your money goes when you buy an L-series lens, we might be able to help you there. We got to see the L-series 16-35mm lens production process, where each lens is individually tested by hand with manually calibrated equipment and a nine-point optical test process.
13 Durability and sensitivity
It’s not enough to produce great optical performance only in the factory because lenses need to be able to maintain this performance through the knocks and hazards of extremes of climate and conditions that photographers put them through. So Canon places great emphasis on durability and what it calls ‘sensitivity’ – this is the lens’s sensitivity to factory production tolerances, temperature extremes, and the typical bumps and bangs of daily use. This sensitivity can be built into the design so that the optical performance is unaffected. An example is the small shockabsorbing ‘bumper’ rings on the front of some L-series lenses.
14 Canon EF 24-70mm lens cutaway
If you want to know why some lenses weigh (and cost) so much, take a look at this: It’s a 24-70mm L-series lens sawn in half through the middle, exposing the
complex arrangement of lens elements, lens groups and cams in the lens barrel.
15 Canon invented the image stabilizer
To this day, this is the achievement that Canon clearly feels a particular pride in. Canon uses lens-based image stabilization rather than the sensor-shift technology used by mirrorless camera makers because of the EOS DSLR design – to stabilize the viewfinder image, you have to stabilize the lens. If the sensor was ‘stabilized’ instead, the optical image in the viewfinder would still be wobbly. Mr Kaneda, head of Canon’s lens product business, did hint that we could soon see the lens and the camera working together to synchronize image stabilization.
16 The widest zoom lens in the world
This is the Canon EF 11-24mm f/4l USM, which offers an angle of view of 117 degrees at its widest setting and has a huge convex front element no fewer than four aspherical elements. We thought that this would have been Canon’s most difficult lens so far to make, but apparently not: “A slight challenge at the beginning,” says Canon Takumi Mr Saito, “but not so much of a difficulty I would say.”
17 BR Blue Refractive optics
Canon uses a variety of new optical materials in some of its specialized lenses, including clever BR (blue refractive) optics. These are not made from regular glass, but an organic material, or resin, developed by Canon. BR lens elements offer strong blue light refraction, and as part of the lens design they can reduce chromatic aberration to a degree not possible with regular glass elements. It’s been used in Canon’s 35mm f/1.4l lens to great effect, which shows little or no chromatic aberration, especially in defocussed backgrounds, where colour fringing can be particularly disturbing.
18 DO optics
You may also have heard of Canon’s DO (Multi-layer Diffractive Optical Element) lenses. These use diffraction grating principles from a particularly technical area of optical science (give us rocket science any day) to help counteract chromatic aberration. Canon’s DO optics reverse the usual refraction of glass elements, so they can be used in combination to correct colour fringing. Canon’s breakthrough was to work out how to combine dual opposing diffractive layers to prevent the light scatter and flare normally associated with diffraction gratings.
19 Delivery by robot
Canon has twenty or thirty of these automated delivery robots at its Utsunomiya factory. They follow the yellow tracks painted on the floor and have automatic collision detection sensors to stop the robots from colliding with things and people.
20 130 million Canon EF lenses and counting
In October 2017 Canon hit a production milestone of 130 million EF lenses. We haven’t carried out a precise calculation because they come in all shapes and sizes, but we reckon if you laid them end to end they would probably stretch half way around the world. Canon announced it had achieved in September the production of 90 million EOS series cameras, which suggests an average of just 1.44 lenses per camera, so it looks like too many users just stick to their camera’s kit lens!