Thanks useful information: 
As many people know, the 24-70/2.8L vs. 24-105/4L IS issue comes up with frightening regularity on photography forums, so I have decided to produce an in-depth study of these two lenses so that people caught in the difficult situation of having to choose between them can go in armed with plenty of information, thus making a more informed choice.
I have written this article on my blog, but have reproduced it here for the benefit of AP members.
I hope it is helpful to those choosing between these two lenses.
Canon Standard L Zooms: 24-70/2.8L vs. 24-105/4L IS
Canon presently offers two L-series, professional-grade, constant-aperture standard zoom lenses:
- Canon EF 24-70mm f/2.8L USM; and
- Canon EF 24-105mm f/4L IS USM.
Very frequently in photography forums, the issue of which lens to choose arises -- often enough that it is worth an entire article to break down each lens's strengths and weaknesses in order to provide an objective assessment.
For some people, choosing between these two lenses is quite difficult, so hopefully the information I provide will help people make the choice that suits their circumstances.
Firstly, let's look briefly at the pros and cons of each lens before going into finer detail.
Canon EF 24-70mm f/2.8L USM - Pros
- one-stop wider aperture (f/2.8 vs. f/4);
- smaller minimum focus distance (0.38m vs. 0.45m); and
- lens hood size suits all focal lengths (more on this later).
Canon EF 24-70mm f/2.8L USM - Cons
- larger;
- heavier;
- more expensive; and
- has less telephoto reach at the long end.
Canon EF 24-105mm f/4L IS USM - Pros
- smaller;
- lighter;
- less expensive;
- has longer telephoto reach; and
- has image stabilisation.
Canon EF 24-105mm f/4L IS USM - Cons
- one-stop narrower aperture (f/4 vs. f/2.8);
- larger minimum focus distance (0.45m vs. 0.38m); and
- lens hood is fixed and designed for the 24mm focal length.
A word of warning: do not look at the number of items in the above lists and draw the erroneous conclusion that more points on the positive side means the lens is a better choice; it is far from that simple, and as is the case with so much in photography, one size does not fit all.
Before going further, let's look briefly at some features common to both lenses:
- 77mm filter thread;
- non-rotating objective element;
- weather sealing;
- rugged construction;
- constant aperture across all focal lengths;
- fast, quiet, ultrasonic focus motor;
- inner/rear focusing;
- full-time manual focus;
- aspherical elements (minimum of two); and
- distance gauge.
Let's now look in further detail at the differences between the features of both of these lenses.
Aperture
The 24-70 offers a brighter f/2.8 aperture (the brightest available in any Canon or Nikon zoom lens), whereas the 24-105's widest aperture is a stop narrower at f/4.
For some people, f/2.8 is the be-all and end-all.
A brighter aperture offers a few advantages; namely:
- the ability to achieve a shutter speed twice as fast;
- easier focusing and composing in lower light; and
- more diffused background blur.
Depending on the type of photography, the need for a faster shutter speed may be paramount. Such photography includes bands, stage performances, weddings or any other photography of moving subjects (mostly people) in dimly lit environments.
Now, the difference between f/2.8 and f/4 is one stop. It could be said that simply increasing the camera's ISO sensitivity by one stop is a legitimate work-around, and in some cases it is. Current DSLRs have much better noise handling than earlier generations, and even at ISO 1,600, some cameras produce very decent results.
Depending on the ambient light, the ISO adjustment may be insignificant (eg, 200 to 400), but when shooting at higher ISO settings such as 1,600, the difference between one ISO setting and the next may be quite significant in terms of sensor-induced noise.
While the same exposure at a particular shutter speed can be maintained by increasing the ISO by one stop to compensate for the one-stop narrower aperture, one thing this cannot do is increase the diffusion of the background blur.
Depth of field is affected by three things: aperture, focal length and subject distance. Where the focal length and subject distance remain the same, the aperture is the differentiating factor, and the difference between f/2.8 and f/4, especially at longer focal lengths, can be quite significant. If background blur is an important quality, the 24-70 would be a better choice.
Similarly, for low-light shooting where people are subjects, the 24-70 would be a better choice.
Focal Length Range
Without a doubt, the 24-105 is the superior lens if having more reach in a single lens is important to the shooter.
However, many people who own a 24mm L zoom also own a 70-200mm L zoom (especially one of the f/2.8 offerings), so to those people, having an extra 35mm may not be a big draw-card.
Where the 24-105's extra (and quite useful) focal range is particularly beneficial is for travel photography. Some travellers may be quite constrained by size and weight, and when travelling, particularly on a non-photographic trip, swapping lenses may not be ideal.
We all know that the main benefit of buying an inter-changeable lens-based camera system is the ability to change lenses, and that buying one lens and never changing it is akin to buying a convertible sports car and always driving with the roof closed; but there are some circumstances in which changing lenses is either impractical or completely undesirable.
A wet or dusty environment is a classic case. When it comes to travel, a traveller may be in a tour group or need to be able to move quickly, and changing lenses could waste time and delay people, or, worse from a photographic perspective, cause the shooter to miss a time-critical shot.
For other people shooting in environments not constrained by size, weight or time, having a separate telephoto zoom lens in the 70-200mm range may mean that the extra 35mm of reach in the 24-105 is not a highly attractive feature that would tip the scales in favour of the 24-105.
Size, Weight and Cost
For many people, the issues of size, cost and weight are significant enough to tip the scales in favour of one lens over the other.
Let's look at the differences between size and weight.
The 24-70 weighs 950 grams, whereas the 24-105 weighs 670 grams. For a lens of this size, that 280 gram difference is substantial.
The 24-70's maximum length is 123.5mm, whereas the 24-105 has a maximum length of 107mm. 1.65cm probably doesn't make a huge amount of difference, but the 24-70 is noticeably longer. It is surprisingly narrower, but by a very small amount (83.2mm vs. 83.5mm).
Cost is variable depending on where you buy and when, but without getting into specifics, the 24-70 is generally going to be $400-500 more expensive in the Australian market. This may be the most significant factor for some people in choosing between these two lenses.
Image Stabilisation (IS)
The presence of Canon's image stabilisation in the 24-105 adds complexity to the decision-making process when evaluating these two lenses.
What IS allows is for up to three stops of hand-holdability. This means that it is theoretically possible to achieve the same shutter speed an f/1.4 lens would allow, and achieve a sharp shot, which makes the 24-105 more desirable than the 24-70.
What's crucially important to understand about image stabilisation is that it is only useful for static subjects; it does not freeze subject movement. The only way to freeze subject movement is with a sufficiently fast shutter speed, which requires more light, or more light-gathering ability.
When shooting static subjects, IS is fantastic. When shooting moving subjects in low light, the only way to achieve a sharp image is with more light, either from flashes, a brighter aperture, a higher ISO sensitivity or any combination of those three factors.
Some people claim that IS is not useful on standard or wide focal lengths. I disagree. I believe that IS is useful at any focal length. It is to be remembered that not all photographers have good lens handling technique, and that a shutter speed for one person may be too slow for another to achieve a sharp image.
IS also helps when instability is introduced by external factors, such as gusty wind, or being on a boat or jetty which may move with the water. IS can also be beneficial when standing on uneven ground or when otherwise placed in an unstable or awkward position on order to land the shot.
If IS is more important than light-gathering ability and subject motion in low light is not a consideration, the 24-105 makes for a better choice.
Minimum Focus Distance
There is an 8cm difference between the minimum focus distance (MFD) of both lenses, with the 24-70 having a shorter MFD at 38cm.
While neither lens could remotely be considered a macro lens (the 24-70 has a maximum magnification of 0.29x at 70mm, and the 24-105 has a maximum magnification of 0.23x at 105mm), it is possible to get quite close to a subject for a larger view.
To that end, the 24-70 is the superior lens because it allows the lens to be closer to the subject, increasing the apparent size of the subject in relation to the frame. Additionally, the f/2.8 aperture allows a narrower depth of field (if this is important to the image).
Lens Hoods
It might seem strange to discuss lens hoods when comparing two lenses, but the differences between the hoods of both 24mm L zooms are significant enough to warrant particular mention, notably because the 24-70's lens hood mechanism is unique to that lens.
The 24-70 has a very large hood that is designed for the 70mm telephoto focal length. How does it work at 24mm? Good question. The hood attaches to the lens barrel, and not the rim of the lens which extends and contracts.
The 24-70 uses a "reverse-zoom" feature, where the lens is physically longest at its shortest focal length. To zoom out to 24mm, the barrel extends. To zoom in to 70mm, the barrel contracts.
Because the hood is not attached to the moving part of the barrel, when zooming out to 24mm, the objective element extends towards the end of the lens hood, and is positioned at a suitable distance from the edge of the lens hood to match the 24mm focal length.
When the lens is zoomed in to 70mm, the objective element is recessed deeply, and the hood therefore provides a greater depth suitable for that focal length.
This is unique to the 24-70; no other zoom lens with an extending barrel (including the 24-105) in the Canon EF lens lineup incorporates this clever design feature.
Because of the lack of this design in the 24-105, its hood is only useful (for preventing flare and increasing contrast) at 24mm. It is a shallow hood, meaning that at 70mm, it is not useful or suitable for the focal length.
I do not consider the hood design of either lens to be a differentiating factor in choosing between the two lenses, but I do consider the "reverse zoom" a very clever and practical design feature, and in the case of the 24-70, flaring is far less likely to be an issue.
But Wait, What About Optical Performance?
Astute readers will have noticed that I have not discussed the optical qualities of both lenses. That alone is a separate subject, and there are plenty of reviews out there, some of which go into considerable detail.
What I will say is this: both lenses are sharp and produce nice colour and contrast. I have not compared in any detail the differences between them, as for my (fussy) liking they are both excellent. Some say the 24-70 is superior, but that's an individual assessment.
I have owned one of these lenses and shot with both; neither one of them left me wanting more image quality.
If the finer points of optical quality are of particular interest, I recommend reading The Digital Picture's Canon EF 24-70mm f/2.8L USM review and Canon EF 24-105mm f/4L IS USM review.
Conclusion
Both lenses are solid performers.
While the individual's needs, wants and constraints are very much variable, I can offer a few general points of advice.
- If low light capability and subject movement is an issue, choose the 24-70.
- If background blur is important, choose the 24-70.
- For general-purpose outdoor/travel photography, choose the 24-105.
- If size, weight and cost alone are limiting factors, choose the 24-105.
Choosing between these lenses is not an easy task, and having been there myself, I can speak first-hand of the difficult choice it is.
Hopefully the points I have discussed here will make it easier for you.
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Originally Posted by twister
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