The reflective characteristics of the image sensors in a digital camera differ from those of film in that they possess a higher reflectivity as well as a characteristic known as regular or “mirror” reflection, which has the effect of creating flaring and ghosting inside the lens when light from a bright source enters the lens and reflects back to the image sensor. In order to resolve this problem particular to digital cameras, a new approach to optical design has already been adopted, with the goal of bringing the outstanding imagining performance of EF lenses to digital photography. This is, after all, the mission of EF lenses in the digital age, because they occupy the core of the EOS system, whether film or digital.

Even when using lenses without built-in protective glass, the particular photographic conditions might mean that using a digital camera will result in more flaring and ghosting than if a film camera were used. If a strong light source is present inside the frame, the light reflected off the image sensor can create complex reflective patterns inside the lens, resulting in flaring and ghosting. To prevent this effect particular to digital photography, we have optimized the shape and coating of f/2.8L zoom series lenses including the EF 16-35mm f/2.8L USM, and other models such as the EF 17-40mm f/4L USM. Specifically, each lens element has a different design, in order to reduce the amount of repeated reflection inside the lens. Further, the lens surface, which has a large effect on reflectivity, is treated with a special multi-layer coating with high transmittance. This allows any light reflected off the image sensor to escape out of the lens in the direction of the subject thus reducing flaring and ghosting. And Canon’s legendary color balance is not compromised, thanks to an exact balance between multi-layer and single-layer coatings.

Players in a stadium or racecars whizzing round the circuit. All are lit up by the bright lighting in the stands, or the headlights on the cars, creating numerous bright light sources. Ordinary super-telephoto lenses have protective glass in front of the first lens unit. If this glass is flat, any light entering the lens from a bright light source will be reflected off the image sensor and back onto the inside of the protective element, causing spot-shaped ghosting. To prevent this, meniscus lenses are used as the protective glass on all of Canon’s large-aperture IS super-telephoto lenses. Meniscus lenses are spherical lenses which have the same curvature on both sides of the lens. By using these lenses as the protective glass, the light reflected off the image sensor forms an image in front of the image sensor and then disperse. Since almost all the light which is dispersed does not hit the reflective elements, this prevents ghosting while at the same time achieving high contrast for the resulting image.

Large-aperture IS super-telephoto lenses used in sports stadiums and racing circuits can now deliver the expressiveness needed by professional photographers using digital SLR cameras thanks to their outstanding imaging performance.

EF 300mm f/2.8L IS USM
EF 400mm f/2.8L IS USM
EF 400mm f/4 DO IS USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS USM
EF 800mm f/5.6L IS USM