Canon EF 24–105mm f/4.0L IS USM

The EF 24–105mm f/4.0L IS USM is an EF mount wide-to-telephoto zoom lens. It was introduced by Canon in 2005 to complement the well-regarded 17–40mm f/4L USM and 70–200mm f/4L USM. The lens is often compared to the other L series zoom of comparable range, the 24–70mm f/2.8L USM, losing one full stop but gaining image stabilization (IS) in return, stabilizing camera shake up to three stops. It also has rubber gaskets for moisture and dust protection, although weather sealing is only effective if the photographer uses a weather-resistant camera body. Some early production models of the lens had a flare problem (reportedly the first 10,000 batch) and Canon offered to repair them for free. On a 1.6x APS-C camera body, this lens' field of view is equivalent to that of a 38–168mm lens on a 35mm film camera; this is a very useful range, covering most normal to medium-telephoto needs.
 

Specs
Optical scheme of Canon EF 24–105L IS USM lens
The lens includes sealing against dust and water, although it is not waterproof. It includes an 8-bladed curved diaphragm which remains nearly circular from f/4 to f/8. Uses common 77mm filters. Characteristic of zoom lenses, it exhibits some barrel distortion at its shortest focal length. This lens is available in kits packaged with the Canon EOS 5D Mk II, 5D Mk III and Canon 6D. The Canon 24-105mm f/4L IS EF USM AF Lens is an easy-to-use standard zoom lens that can cover a large zoom area ranging from 24mm wide-angle to 105mm portrait-length telephoto. The EF 24-105mm f/4L IS USM incorporates Canon's highest standards of precision optics. The L-series is Canon's flagship professional lens range, combining outstanding image performance and ultimate operability with dust and moisture resistant construction.

Canon's ring-type USM gives silent but quick AF, along with full-time manual focus. Moreover, with dust- and moisture-resistant construction, this is a durable yet sophisticated lens that meets the demands of advanced amateur photographers and professional photographers alike.

Fixed Aperture
    With no change in aperture over the full focal length range, photographers can set exposure at the widest aperture and zoom through to 105mm without slowing shutter speed. 

Image Stabilizer
    Ideal for handheld work, IS Image Stabilizer allows use of shutter speeds up to 3-stops slower with no perceptible increase in image blur.

Super UD and Aspherical Lens Elements
    Constructed with one Super-UD glass element and three aspherical lenses, this lens minimizes chromatic aberration and distortion. The result is excellent picture quality, even at wide apertures.

Super Spectra Coatings
    Optimized Super Spectra lens coatings and lens element shaping suppress flare and ghosting - more prone to occur with digital cameras due to reflection off the image sensor. Coatings also help achieve true color balance and increase contrast for vivid hi-fidelity images.

Ring USM
    Ring USM (Ultrasonic motor) uses ultrasonic frequency vibrations to drive responsive, near-silent high speed auto focus. Good holding torque stops the focusing lens group with precision without overshoot. Full time manual focus override is available without having to switch out of AF.

The Canon EF 24-105mm f/4 USM L IS was an eagerly awaited lens since the old film days. On full frame (D)SLRs it is surely a near-perfect standard zoom with a 4.4x zoom ratio in combination with a relatively compact size, a relatively low weight and an image stabilizer on top. Some may not like the rather modest max. aperture but then there's always a trade-off somewhere with all zoom lenses. With a weight of 670g and a size of 84x107mm it is quite a bit more compact and light-weight than the EF 24-70mm f/2.8 USM L. Unlike its cousin the lens has a conventional zoom mechanism so it extends towards the long end of the range. While this feels right somehow the lens hood (part of the package) isn't quite as efficient because it was only optimized to the 24mm setting of the lens. The front element does not rotate during focusing so there're no issues when using a polarizer - without hood at least.

On APS-C DSLRs its field-of-view resembles a classic 39-168mm lens on full-frame cameras so by most standards things aren't quite as interesting here as on a full frame DSLR/SLR. The lens is also sold as a kit lens in combination with the Canon EOS 5D where it certainly makes more sense due to the full frame image sensor of the camera. The lens has a ring-type USM drive based on a front-focusing system resulting in an extremely fast AF speed and extremely low AF noise. Full-time manual focusing (FTM) is always possible in one-shot AF mode. The optical construction is made of 18 elements in 13 groups including three aspherical elements (two replica, one glass molded) plus one S-UD (super ultra-low dispersion) element. The min. focus distance is 0.45m resulting is a max. object magnification of ~1:4 at 105mm. The lens features 8 circular aperture blades. Typical for most Canon L zooms the filter size is 77mm.

The image stabilzer provides an equivalent effect of a 3 f-stops gain in shutter speed for hand-held photography (at cost of slower shutter speeds if exploited to the max). The IS works for static scenes only so there's no 2nd mode for panning. Regarding the nature of the lens this isn't a big drawback because action photography is normally not a primary application. It is worth to mention that this lens has been serviced by Canon due to the flare problem present in very early production lenses. The build quality of this lens is exceptional. No significant wobbling and smooth control ring - almost perfect. The lens is also designed to survive in harsh conditions with a sealing against dust and moisture.
 

The 24-105 L's color and contrast are excellent. The rectangular baffle (above) over the rear of the lens is purposed to increase contrast and reduce flare/ghosting. CA (Chromatic Aberration) is well controlled with some CA visible in area harsh contrast primarily at full-frame edges at both ends of the focal length range. The 24-105 L features a reasonably fast widest aperture setting of f/4 which remains constant throughout the zoom range. This lens rounds out Canon's f/4 zoom lens line - Up to 200mm at least (many of us would like to see a Canon's f/4 zoom lens line extended to include an EF 200-400mm f/4 L IS USM Lens).

Eight circular aperture blades provide excellent quality defocused image quality (bokeh - foreground/background blur). While f/4 in this focal length range is not the best at creating diffusely blurred backgrounds, close subjects at 105mm can have pleasingly blurred backgrounds. Canon's latest generation Image Stabilizer (IS) provides an additional 3-stops of handholdability in the 24-105 L. This is definitely one of my favorite features of the 24-105 L. The 24-105 L's IS is very quiet and very well behaved (does not jump when starting, ...). IS does not stop subject motion blur, but it is excellent for stopping camera shake. IS allows use of narrower aperture settings to increase DOF (Depth of Field) in handheld shots with non-moving subjects (landscapes, sculptures, art ...). IS allows use of longer shutter speeds to create motion blurs - such as moving water. Or simply shoot handheld in low light levels with the lens wide open using IS to steady the shot.

Theoretically, IS enables this lens can be shot handheld at shutter speeds as low as 1/3 second at 24mm on a full frame body. Your results will depend on how steady you are, but I am seeing sharp shots at 1/3 second (and many longer) at 24mm and 1/6 second (and longer) at 105mm. Very nice. A tripod was not used for most of the 24-105mm sample pictures (link below) with shutter speeds below 1 second. I would unscientifically rate this lens as delivering a keeper rate as high or higher than any lens I own or have owned. And most of my throw-aways are the fault the person behind the lens.

Conclusion

This is the big Kahuna of normal zooms. It's well made and tack sharp. I love the range, AF speed, sharpness and feel of this lens. It balances well on larger bodies such as the EOS 3 or 5D Mark II but is front heavy on a Rebel. Yes, the largest aperture of F4 is slow, but the 3-stop IS almost makes up it. While not a small or light lens, it is my favorite optic for travel due to a near perfect balance of image quality, range and versatility. Regarding its equivalent zoom range (39-168mm) on an APS-C DSLR the Canon EF 24-105mm f/4 USM L IS may not be the most sexy lens here but its performance figures are very impressive nonetheless. In fact the resolution results beat those from the EF 24-70mm f/2.8 USM L and match the EF 28-70mm f/2.8 USM L with its much more conservative zoom range (but higher speed). There's a slight decrease in performance at 105mm but even here the quality remains on a very high level. As to be expected from a modern Canon L lens the construction quality is up to pro standards matching its fasters cousins. The lower price tag plus the extra IS should compensate the slightly more moderate max. aperture for most users. Is it a perfect lens then ? Well, there're also downsides like pronounced barrel distortions and higher than expected CAs at the wide-end of the zoom range. However, the package remains extremely attractive if you can live with the rather unattractive zoom range on an APS-C DSLR - similar to other 28-xx or 24-xx zooms this lens is really more meant for 1.3x or FF (D)SLRs.  Price: $1,149.00