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Canon EF 17-40mm f/4L USM Ultra-Wide Zoom – Excellent Quality at Half the Price ⭐⭐⭐⭐⭐

May 26, 2013

Canon EF 17-40mm f/4L USM Ultra-Wide Zoom – Excellent Quality at Half the Price of Canon’s 16-35mm "L" version

A new and affordable L-series ultra-wide-angle zoom lens that’s ideal for both digital SLRs and film cameras. Superior optics are assured by the use of three Aspherical lens elements, in addition to a Super UD (Ultra-low Dispersion) glass element. Optical coatings are optimized, front and back element surfaces, for use with digital cameras, to prevent backward-reflectance eminating from the relatively “shiny” imager’s surface.

⚫ Canon EF 17-40mm f/4L USM Lens focuses as close as 11 inches (0.28m), and offers both Canon’s full-time manual focus and a powerful ring-type USM for fast and silent AF. It has a constant f/4 maximum aperture, and offers the choice of screw-in 77mm filters or a holder in the rear of the lens for up to three gel filters. Finally, it offers weather-resistant construction similar to other high-end L-series lenses.

⚫ Canon EF 17-40mm f/4L USM Lens is especially well suited for use with EOS digital SLR cameras, which usually have an imaging sensor size smaller than the 35mm format. When used with such digital SLR cameras, the 17-40mm focal length range gives an angle of view approximately equivalent to that of a 27-64mm lens upon 35mm cameras, making it an ideal medium-aperture standard zoom lens.

⚫ Canon EF 17-40mm f/4L USM, like all of the Canon “L” lenses, delivers optical performance equal to similar fixed focal length lenses, with silent, high-speed focusing. Distortions and aberrations are remarkably small for a lens of such amazing capability. It combines 1 high-precision molded glass aspherical lens and 2 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.

⚫ Canon EF 17-40mm f/4L USM 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 of the size of the lens. 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.

⚫ Canon EF 17-40mm f/4L USM Lens is a Canon ‘EF’ series lens, indicating it is for use with full-frame cameras. It works equally well with APS-C and APS-H imager-formated Canon DSLR cameras.

⚫ Canon EF 17-40mm f/4L USM Lens, an autofocus super wide angle zoom lens for digital cameras. Produces 27-64mm equivalent focal length with “APS-C” size digital EOS SLR cameras (such as the EOS 20D, EOS 30D, EOS Digital Rebel, EOS 50D, etc.)

⚫ Uses 3 aspherical lens elements and Canon

⚫ Super UD ultra-low dispersion glass

⚫ Provides professional levels of moisture and dust resistance

⚫ Internal zooming and focusing

⚫ Circular aperture diaphragm for better, natural looking background blurring

⚫ Accepts 77mm filters, as well as gelatin filters upon the rear of lens

⚫ Focal Length & Maximum Aperture 17 – 40mm; 1:4

⚫ Lens Construction 12 elements in 9 groups

⚫ Diagonal Angle of View 104° – 57° 30′

⚫ Focus Adjustment Inner focusing system with USM

⚫ Closest Focusing Distance 0.28m / 0.9 ft.

⚫ Zoom System Rotating type

⚫ Filter Size 77mm

⚫ Max. Diameter x Length, Weight 3.3″ x 3.8″, 1.1 lb. / 83.5 x 96.8mm, 500g

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Available Retail Price: $699. Canon Suggested Retail Price: $839.99

Canon Item Code : 8806A002

Operating Manual:

The Key for Interpreting MTF Charts, Modulation Transfer Function Charts: Recall, the higher Up the chart a line is, the higher the contrast, and that 0 to 20 across the bottom scale represents the distsance in millimeters from the center of the lens to its edge. Ignoring the dotted vs. dashed lines for the moment. Here is some guidance in reading MTF Charts:

✔ The higher UP the chart the 10 LPM line is (the thick lines), the higher the contrast reproduction capability of the lens will be.

✔ The higher UP the chart the 30 LPM line is (the thin lines), the higher the resolving power and thus subjective sharpness of the lens will be.

✔ The solid black lines show the lens wide open, f2.8 the maximum aperture.

✔ The solid blue lines show the lens stopped down to exactly f/8 for all lenses.

✔ The closer each paired-sets of solid-lines are to each other within the pair, the better the performance of the lens when used at its maximum aperture of f2.8 for this particular lens.

✔ The closer the the dotted and dashed line-pairs on the MTF chart, are to each other, the more pleasing the Bokeh of the lens. Meridonial and sagital lines are also used used to evaluate astigmatism distortion and field curvature.

✔ The very best performing lenses will have the Black and the Blue lines closer together. The further apart the Black and Blue lines are, the lens would be of lesser overall performance

✔ The lens whose thick lines (10 LPM) are above 0.8 (or 80%) on the chart should be regarded as having excellent image quality. Values above 0.6 (or 60%) is regarded as “satisfactory”. Line-values below 0.6 (or 60%) may be considered below satisfactory.

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