Constant f/2.8 maximum aperture

The Canon EF 1635mm f/2.8L III USM has a bright and fast constant maximum aperture of f/2.8, which provides superb control over depth of field, great low light performance, and the ability to maintain the same aperture throughout the zoom range to make manual exposure operation a breeze. The lens is particularly helpful when shooting outdoors at dusk or in inclement weather, or indoors in dimly lit rooms. At f/2.8, the EF 1635mm f/2.8L III USM offers a bright view when composing images using the cameras viewfinder.

All-new optical design

The EF 1635mm f/2.8L III USM features a new optical design engineered to deliver images of remarkable clarity and depth a magnificent complement to the large, high-resolution sensors in the SLRs favoured by todays advanced photographers. It employs two large-diameter double-surface GMo lenses plus a ground aspherical lens to help decrease distortion, curvature of field and astigmatism. Two UD lenses help to reduce chromatic aberration, leading to precise colour rendition, accurate edge-to-edge detail plus excellent contrast throughout the lenss zoom range. This means sharp landscapes, reduced distortion in the edges of the frame and an overall improvement in image quality no matter the subject.

Subwavelength Coating (SWC) and Air Sphere Coating (ASC) help to significantly reduce flare and ghosting

The EF 1635mm f/2.8L III USM features both Subwavelength Coatings (SWC) and Air Sphere Coatings (ASC) on its lens elements to help combat reflections, flare and ghosting, and deliver clean images with reduced aberrations from reflected light. Subwavelength Coatings help prevent reflections by arranging an array of wedge-shaped nanostructures on the lenss surface that are smaller than the wavelength of visible light and are able to help control reflection and flare. Air Sphere Coating technology puts an ultra-low refractive layer on the lens element designed to significantly reduce both flare and ghosting. These coatings, in concert with the EF 1635mm f/2.8L III USMs overall optical formula, help to deliver a clean image to the cameras sensor, which can decrease the need for post-production.

Dust- and water-resistant construction

Befitting an L-series lens, the EF 1635mm f/2.8L III USM is built to endure photography and moviemaking in even the harshest conditions*. It features a dust- and water-resistant construction on the switch panel, the zoom and focus rings, and on the lens mount, helping to prevent dust and moisture from interfering with operation. When outfitted with a Canon filter, the EF 1635mm f/2.8L III USM is supremely dust- and water-resistant.
* Full weather-resistance for front section of lens requires attaching an optional Canon PROTECT filter.

Circular aperture (9 blades) helps deliver beautiful, soft backgrounds

Thanks to a 9-bladed circular aperture, the EF 1635mm f/2.8L III USM can create remarkable evocative out-of-focus areas and soft backgrounds. Its f/2.8 maximum aperture provides an exceptional level of control over background blur, which helps you define the mood of your image, creating powerful imagery.

Inner focusing, ring USM, high-speed CPU and optimized AF algorithms for fast and accurate autofocusing

The EF 1635mm f/2.8L III USM is engineered to provide fast, accurate operation for efficient performance across the board. It features a high-performance control CPU that drives Canons quick inner focusing with ring USM for quick starts and stops. Plus, its programmed with optimized AF algorithms that help achieve fast, accurate focus and maintain it consistently.

Full-time manual focus allows manual focus adjustment while in AF Mode

The EF 1635mm f/2.8L III USM offers complete manual control, even when AF is engaged, with a simple twist of the lenss focus ring. Additionally, full-time manual focus means its easy to achieve and maintain focus manually, which can be especially handy when shooting video or composing still images on an SLRs screen.

Fluorine coating on front and rear lens surfaces helps reduce smears and fingerprints

To help maintain a clean lens, even after multiple lens changes in sub-optimal conditions, the EF 1635mm f/2.8L III USM has a specially designed non-stick fluorine coating on its front and rear surfaces. This fluorine coating helps prevent dust, water, oil and other surface residue like fingerprints from sticking to the lens, resulting in quick and easy wiping, without the use of solvents.

• Canon EF 16-35mm f/2.8L III USM Lens
• E-82 II 82mm Lens Cap
• Lens Dust Cap E (Rear)
• EW-88D Lens Hood
• LP1222 Lens Pouch