Canon EF 24-105mm f/4L IS USM: Great investment.

It's been over two years that my trusted EF-S 17-85 mm took the role of the universal lens and has been only recently deemed inadequate. The changing event was my upgrade from a 8 MPx camera (20D) to a 10 MPx camera (EOS 40D). Granted, the increase is only realistically 8% in resolution, but the smaller pixels made lens "softness" or aberration more visible and the cry for an "L" lens was loud and clear. A month and 1000 photos later, this turned out to be the best investment in this configuration. In hindsight, the 20D could have easily profited from the better lens as well.


EF 24-104mm vs EF-S 17-85mm

Technically, this is a comparison of apples and oranges for two major reasons. The f/4L in the EF 24-105 describes low dispersion glass and a constant maximum aperture while the EF-S 17-85 is not only a variable aperture up to 5.6 at higher zoom levels, it's also standard quality glass which isn't necessarily bad (at least not by default), but still a sometimes significant difference. The 24-105 lens sports a slightly more versatile zoom range, but looses a bit on the wide angle. The EF-S lens is smaller and lighter, but also prone to more lens related aberrations and essentially not as sharp (contrast) either. However it costs half the money the "L" lens lists for.

In essence, the EF-S 17-85mm is a good lens at a great price point. The 24-105mm is a fantastic general purpose lens with only price and some weight held against it. Nevertheless, it's a great investment as a good lens typically lasts a lot longer than any given camera body. (Provided it meets requirements of digital photography like AR coating etc..)


IN A NUTSHELL

The "L" is the main reason to consider this lens as "low dispersion" directly translates into sharper images at today's pixel density (by rendering minute details), which in the "film" days would have been lost in grain. In fact, many claims that a certain camera produces "soft" pictures are founded in the lens and consumer-grade glass is often not good enough to utilize the resolution of the sensor (especially when the sensor is smaller).

The 24-105mm focus range is quite versatile in normal applications for full frame sensors (i.e. EOS 5D), but also for APS sized sensors despite the lack of wide angle (APS-C as in the EOS 40D). What the smaller sensor looses in FOV, it compensates with more "reach" and reduced aberration since it avoids the extreme angles by utilizing only the center. Further, ultra-wide lenses often introduce aberrations by attempting to cover too broad of a range. The 24 mm of this lens is a respectable wide angle for the 5D et.al. and still manages to keep distortion low.

The optical quality of the glass as well as a constant aperture (f/4) across the whole range sign responsible for good contrast (resolution) for a zoom, but it's also obvious in the size and weight of the lens. Nevertheless, finally you'll be able to produce sharp pictures with a reasonably priced zoom (considering the cost of a f/2.8 zoom with a similar range).


DETAILS

Construction: [*****] - The build quality of metal housing matches the professional price and is very robust. The extending front element is a tight fit with the body and very little movement is allowed to maintain a sharp image across the whole area. Further, the typical lens creep (when pointing downwards) is practically eliminated. All this results in a rather large and heavy lens (for a universal) and in regard to the 40D, it simply doubles the weight to a "hefty" 1.5 kg, but on the bright side that also makes for more stable holding (until your arm gets tired). Add battery grip and external flash (i.e. Speedlite 580EX II) and it becomes a workout. Either way, the weather seal of course only works in conjunction with a sealed body, but provides extra protection for non-ideal shooting conditions (to keep the lens from fogging up inside).

Speed: [****-] - While the maximum aperture is often used to describe the "speed" of a lens (due to allowable shutter speeds), the maximum aperture of f/4 isn't enough to activate the precision focus on most Canon dSLRs including the 40D, but it's plenty fast to have all cross sensors active (requires f/5.6). Another kind of speed is the focusing speed and the included ultrasonic motor manages to bring subjects in quickly in focus while generating virtually no noise (other than a faint "swish").

Image Stabilization: [****-] - What used to be a perk turned virtually into a must feature. The improvements range between 2 and 3 stops and that simply means that at f=105mm one can successfully use this lens up to 1/25 sec or even 1/13sec and still yield similar sharpness in handheld shooting as 1/100 sec would. Alternatively, for landscape shooting this would need that the aperture can be an f/8 instead of a f/5.6 under the same lighting and yield better depth of field. However, at 3 stop effectiveness it's one stop less than Canon's latest models, but that's nothing a tripod couldn't fix.

Sharpness: [****-] - A zoom lens typically has to make compromises between distortion, color fringing and contrast (sharpness) at different focal lengths. (A fixed lens is typically far superior to any Zoom as it doesn't have to compromise.) Anyway, the design and glass quality of the EF 24-105 f/4L is visible in the improved sharpness across the zoom range and while not a match for a good fixed lens, it comes pretty close within the requirements of a 10 MPx APS-C sensor with 5.x um pixel size. The amazing part about the "L" lens is that the sharpness is maintained virtually across the field of view. This is mostly a result of the lens quality, but is also a benefit when using a FF lens on a smaller sensor (in my case the 40D).

Chromatic Aberration: [****-] - The dreaded color fringes are an optical problem of separating colors due to the physical lens design making compromises and really being optimal for a certain wavelength only. Typically, the more elements, the greater the aberrations. The EF 24-105mm f/4 L does a great job in keeping those artifacts minimal and is typically limited to the outer range of the FOV anyway. Compared to the EF-S 17-85mm IS lens, the color fringes are significantly less pronounced and in some cases even eliminated. This is a good argument for choosing 24mm as the widest angle, and leave the lower range to a dedicated wide-angle lens (i.e. the EF-S 10-22mm).

Macro: [***--] - While there is a macro mode to allow approaching a subject as close as 0.45m, combined with a focal length of 105mm the achievable magnification turns out to be 0.23x (without any extension tube). Using the Canon EF12-II extension tube improves the macro capabilities to 0.6x magnification at 24mm and 0.4x at 105mm without significant distortions. This is still a far cry from a dedicated 1:1 (1.0x) macro lens (i.e. Canon EF-S 60mm f/2.8 USM, but often quite manageable for typical applications like flower shots.

Inner Focus [*****] - Generally a common feature for this lens class, inner focus basically allows to keep the lens end in a constant position while focusing. Since the filter mount doesn't rotate either, the use of rotation sensitive filters like a Circular Polarizer is unaffected. (The importance of a front part -- or filter mount -- that doesn't extend and rotate during focus can best explained with close-up filters and C.Pl. filters.)

Bokeh: [*****] - As one should expect from this price range, the included eight circular aperture blades provide excellent quality background blur, a.k.a. bokeh). Of course the maximum aperture of f/4 better at 105 mm than the 24 mm to render pleasingly blurred out-of-focus blur. Highlights are nearly round and well defined, another quality feature of this lens.

Accessories: [****-] - Two vital add-ons are actually already included (as with most professional grade lenses from Canon): a hood and a pouch. The tailored hood (EW-83H) prevents stray light to enter the lens at extreme angles outside the FOV and cause unwanted reflections. The jury is divided on the necessity of a UV filter, as a bad one can actually hurt the image more than it helps (with additional flare and reflections), but of course that may be secondary when the front lens gets scratched. Hence, a high-quality UV filter like Hoya's Pro-1 series is recommended to (1) protect the lens and (2) keep unwanted reflections to a minimum. The 77mm size is a significant factor though, and mentioned filter is almost $100. The size also adds to another vital filter (that can reproduced only in limited fashion by post-processing) is the circular polarizer. Same implications apply and the Pro-1 actually costs a whopping $200 in this size, but it's worth it for managing artifacts that are typically introduced by adding low quality filters.

Value: [****-] - There is no question that $1000 is a lot of money for a lens, especially when the camera body cost almost the same. Photographers know that the real investment is in good lenses and the body is often secondary (but not unimportant). The EF 24-105mm f/4L IS USM is a great compromise between the affordable and lightweight consumer grade lenses (like the EF-S 17-85mm) and the fast and heavy professional lenses (like the EF 70-200mm f/2.8L IS). Once you see the improvements over the consumer grade lens and don't need the fast action of a f/2.8 lens, the EF 24-105mm f/4L is a great lens that easily outlasts your current camera body and possibly the next.

© 2007, theuerkorn

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