A fantastic all-round lens!
The Canon EF 24-70mm f/2.8 USM L is one of mainstream pro grade lenses in the Canon line up and very popular among pro photographers (especially press) as well as serious amateurs. On APS-C DSLRs its field-of-view resembles a classic 39-112mm lens on full-frame cameras which isn't terribly useful to start with. Here it shows that this lens was designed for full-frame (D)SLRs.
With a weight of 950g and a size of 83x123mm it is quite a bit heavier and bigger than many third party alternatives but comparable to similar lenses made by other genuine brand manufacturers.
The lens has a reverse zooming mechanism so it extends towards the wide end of the range. It is shortest at 70mm. While this may seem odd at first the system makes sense when attaching the deep flower-shaped hood which remains highly effective at all focal lengths. So with attached hood the size of the package remains constant. The front element does not rotate during focusing there're no issues when using a polarizer - without hood that is.
The optical construction is made of 16 elements in 13 groups, including one UD elements and two aspherical elements. The elements are made of lead-free glass. The min. focus distance is 0.39m resulting is a max. object magnification of ~1:3.3 at 70mm. The lens features 8 circular aperture blades. The filter size is 77mm.
The lens has a ring-type USM drive based on a front-focusing system resulting in an extremely fast AF speed. As usual for modern ring-type USM lenses full-time manual focusing is always possible in one-shot AF mode.
The build quality of this lens is exceptional. No significant wobbling and smooth controls - almost perfect. The lens is also designed to survive in harsh conditions with a sealing against dust and moisture.
Technologies
Aspherical Lenses
Canon’s aspherical lens elements converges central and peripheral light rays at a single focal point to ensure uniform sharpness and clarity over the whole image area. Now found in almost every EF lens, aspherical lens elements are particularly useful for large-aperture lenses, wide-angle lenses and high quality compact zoom lenses.
UD Lenses
UD (Ultra Low Dispersion) lens elements incorporate low-dispersion optical glass which minimizes distortion and chromatic aberration.
Ultrasonic Motor (USM)
Canon's Ultrasonic Motor (USM) is a lens-based motor to harness ultrasonic oscillation energy. This technology makes focusing precise, virtually noiseless and incredibly quick – some lenses focusing literally faster than the human eye. The USM starts instantaneously and stops the moment focus is achieved, with no overshooting. What's more, the USM requires minimal battery power so you can shoot for longer on a single charge.
Specifications
35mm equivalent focal length range: 38-112mm
Lens perspective: Wide to Short Telephoto
Minimum aperture: f22
Image stabilisation: In-Camera Stabilisation
Ultrasonic motor: Yes
Special lens elements: 2 Aspherical Lens Elements and a UD Lens Element
Filter size: 77mm
Weight: 950g
Dimensions: 83.2 x 123.5mm
Maximum magnification: 0.29
Recommended applications: General use, Portraits, Fashion
