For decades, telephoto zoom lenses have been divided into two categories. Budget-friendly consumer models are reasonably compact and tend to have a maximum aperture of f/4-5.6 as you stretch through the zoom range. Professional lenses are bigger, heavier, have higher-grade optics and usually boast a faster maximum aperture of f/2.8 or f/4. The maximum aperture also remains ﬁxed throughout the zoom range, earning them the ‘constant-aperture’ moniker. The new Canon EF 70-300mm f/4-5.6L IS USM breaks the mould.
Despite having a fairly modest ﬁlter diameter of 67mm, 10mm less than the fast EF 70-200mm f/2.8 L IS II USM lens, the lens barrel is almost the same width. At ﬁrst the 70-300mm L looks like a budget telephoto zoom packed into an oversized full metal jacket.
Look deeper, though, and you’ll ﬁnd a full raft of Luxury-series ﬁnery. Build quality feels rock solid, there’s full environmental sealing to guard against moisture and dust in adverse shooting conditions, and all switches and moving parts feel of fully professional quality.
A weighty issue
The zoom ring is silky-smooth, without any hint of stiffness, but there’s no zoom creep. Even so, the lens features a zoom lock switch, to be on the safe side. The ring-type USM (UltraSonic Motor) autofocus is wonderfully fast, quiet and precise, and features full-time manual override to tweak the focus if needed. The minimum focus distance of 1.2m is ﬁxed throughout the zoom range, giving a maximum magniﬁcation of 0.21x at 300mm.
The battleship build quality inevitably has an impact on weight. The all-plastic EF-S 55-250mm IS lens, which performs very well on APS-C cameras such as the 550D, 60D and 7D, weighs a mere 390g; the 70-300mm L is more than 2.5 times as heavy, at 1.05kg. Despite the extra bulk and weight, handling feels very natural, even on lightweight bodies like the 550D. And while the 70-300mm L is fully compatible with full-frame cameras such as the 5D Mark II, it gives really powerful telephoto reach on cameras with smaller sensors, with an effective zoom range of 112-480mm.
The main strength of a faster telephoto lens, with a larger maximum aperture, is that you can fend off camera shake and freeze the action with a faster shutter speed. Conventionally, you’d need a minimum shutter speed of 1/500 sec to avoid camera shake at an equivalent focal length of 480mm. Using an EF 70-200mm f/2.8L IS II USM with a 1.4x teleconverter, you’d get a maximum equivalent telephoto length of 448mm, with a one-stop faster aperture of f/4. However, this combination would set you back over £2,000 – getting on for twice the price of the 70-300mm L.
To beat camera shake, the 4-stop image stabiliser on the 70-300mm works brilliantly well. On a 550D, we consistently got pin-sharp handheld shots at an equivalent 480mm focal length, shooting at just 1/30 sec. It’s actually a dual-mode stabiliser: Mode 2 applying stabilisation in just the vertical plane when panning in landscape-orientation, and vice versa when panning in portrait-orientation.
Naturally, no amount of stabilisation can counteract movement on the part of the subject but, then again, current Canon D-SLRs offer excellent image quality at higher ISO ratings, so it’s relatively painless to offset the lens’s smaller maximum aperture by increasing the camera’s sensitivity. The other bonus of wider apertures is that you can minimise depth of ﬁeld, but 300mm at f/5.6 still enables you to go really shallow.
The bottom line is image quality, and the 70-300mm L really excels. Distortions are remarkably low for a zoom lens and chromatic aberrations are practically non-existent. The biggest factor, however, is that an expensive lens like this with a relatively modest maximum aperture really has to deliver super-sharp shots with plenty of contrast when shooting wide open. Whereas we’d expect to need to shrink the aperture to f/8 or f/11 for good image quality with most budget telephoto zooms, the 70-300mm gives premium quality at its maximum apertures.
Read more: http://www.photoradar.com/reviews/product/canon-ef-70-300mm-f4-5-6l-is-usm-review#ixzz1EhpQAaoB