The EF 17‎-40mm f/4L USM Lens from Canon is a high quality ‎"‎L‎"‎ series wide angle zoom lens for full frame and APS‎-C size DSLR cameras‎.‎ It combines one high‎-precision molded glass aspherical element and two replica aspherical lenses to achieve the extended zoom range‎,‎ while also correcting for common aberrations that arise during zooming‎.‎ A Super UD ‎(‎Ultra‎-low Dispersion‎)‎ glass element minimizes the chromatic aberration of magnification which tends to occur with wide‎-angle lenses‎,‎ to help eliminate color bleed along the edges of the subject and achieve high image contrast and resolution‎.‎

The lens‎'‎ minimum focusing distance is just 11‎"‎ ‎(‎28cm‎)‎ throughout its entire range of focal lengths‎,‎ which makes it very useful for close‎-up work‎.‎ All of the focusing and zooming action is done internally‎,‎ with no changes in the size of the lens‎.‎ Its ultrasonic autofocus motor enables smooth and silent autofocus action and manual focus override in One Shot AF mode allows precise manual focusing without switching into MF mode‎.‎

It only uses lead‎-free optics to help the environment‎,‎ and features a circular diaphragm for improved background blur‎.‎ The housing is water and dust resistant to help ensure reliable performance for both professionals and enthusiasts‎.‎ Like many ‎"‎L‎"‎ lenses‎,‎ it uses 77mm filters‎,‎ but also has a rear gelatin filter slot behind the lens mount that can hold three gel filters‎.‎

This lens is a Canon ‎'‎EF‎'‎ series lens‎,‎ indicating it is for use with full‎-frame cameras‎.‎ However‎,‎ it also works with APS‎-C format DSLRs and offers a 35mm focal length equivalence of 27‎-64mm‎,‎ making it an ideal medium‎-aperture standard zoom lens‎.‎

A super wide‎-angle zoom lens for full‎-frame DSLR and 35mm film cameras that offers a 27‎-64mm focal length equivalent when used on APS‎-c size sensors‎.‎

Uses three aspherical lens elements and Canon Super UD ultra‎-low dispersion glass for reduced aberrations and overall sharp‎,‎ high contrast imaging

An ultrasonic autofocus motor provides fast‎,‎ smooth and quiet AF action‎,‎ particularly important when shooting video‎.‎

Manual focus override enables precise manual focusing even when in One Shot AF mode‎.‎

Internal zooming and focusing systems

As a Canon ‎"‎L‎"‎ series lens it provides professional levels of moisture and dust resistance‎.‎

Circular aperture diaphragm for better‎,‎ more natural looking background blurring

Accepts 77mm filters‎,‎ as well as gelatin filters at the rear of the lens‎.‎

Performance

Focal Length     

• 17 ‎- 40mm

Comparable

• APS‎-C 1.6x Focal Length‎:‎ 27 ‎- 64 mm

Aperture            

• Maximum‎:‎ f/4
• Minimum‎:‎ f/22

Camera Mount Type     

• Canon EF

Format Compatibility   

• 35mm Film / Full‎-Frame Digital Sensor
• Canon ‎(‎APS‎-C‎)‎

Angle of View  

• 104° ‎- 57° 30‎'‎

Tilt/Shift             

• None

Minimum Focus Distance           

• 11.02‎"‎ ‎(‎28 cm‎)‎

Magnification  

• 0.24x

Maximum Reproduction Ratio

• 1‎:‎4

Elements/Groups           

• 12/9

Diaphragm Blades          

• 7

Features

Image Stabilization        

• No

Autofocus          

• Yes

Tripod Collar     

• No

Physical

Filter Thread     

• Front‎:‎77 mm