I'm considering getting one or the other of these lenses (to use mainly on a 40D, replacing a Canon 28-135 IS). Michael Reichmann compared the two a couple years ago and seemed to conclude that, on balance, the 24-105 had slightly better image quality. Most other professional reviews I've seen come to the opposite conclusion. User reviews on retail sites, Fred Miranda, etc are all over the map. (I realize user reviews are often just that - more about the user than the product, but even selecting the more thoughtful reviews it seems there's a wide range of experiences.) So I'm looking for opinions here, especially from people who have used both. I'm concerned with image quality from the standpoint of acutence, resolution and color - not so concerned about distortion. Focal length range, size, weight, etc will affect my decision only if image quality seems like a toss-up. Or if anyone thinks I'd be wasting my money and should keep my 28-135 I'd like to hear those opinions too.
Thanks

About the 24-70 vs 24-105
It is my opinion having used both that the 24-70 is optically better, the 24-105 is an all-terrain that is nice as a kit lens but certainly not in the same league as the 24-70 in terms of resolution, color and IQ in general.
I wouldn't hesitate to recommend the 24-70 over the 24-105

About keeping the 28-135
The 28-135 varies a lot from copy to copy, if yours is a really good copy then it might make sense to invest in something else. I've owned 3 28-135 and the best one was really sharp, I regret selling that great copy but I needed the money and it wasn't a lens that I used a lot.
If you have an average or bad copy of the 28-135 then the 24-70 will be better by many miles.

Luigi

I have the opposite experience. I own both the 24-70 and the 24-105, and shoot them on 1DsMKIII, 5D and 450D. I can't tell you the last time the 24-70 was out of the camera bag, at least a year. The IQ is quite similar, at least to my eyes, and on the usefullness scale the 24-105 wins hands down.

There have been some good threads on exactly this subject quite recently. It might be worth having a search. The consensus as I remember is that they both have pros and cons and it just depends on your needs.

My experience with FF sensors is that they both have good image quality. Other points are -

24-105 - Lighter, wider focal length range, image stabiliser.

24-70 - One stop wider aperture, deep lens hood is much better against the light.


Jim

I shot with both (1d2, 5D, 1Ds3) and kept my 24-70 f/2.8 in the end. The image quality was identical or very close with a small edge in favour of the 24-70. I have to say that the 24-105 f/4 was also a pleasure (IS & light weight) to use but the distortion at the wide end was a problem for me.

I think it would really help to know what you will be shooting the most of.

The 24-105mm lens is good for landscapes and studio work.
The 24-70mm lens is good IF, and that is a big IF, you can get a sharp copy. I had 2 versions of this lens and both were too soft for my liking. There is this guy Toshio with TC Camera Repair (I want to say... Cannot remember for sure) who calibrated that second version of mine with my 5D and made it a lot better! I mean A LOT BETTER. It cost like $150 but it was well worth it.

I just sent him the lens and body and let him work his magic. All in all it took about a week to ship and get back.

I don't care what lens you have, it will be the sharpest a couple stops down, if you are using the lens more for landscapes then the 24-105 will be where it's at because you will be in the f/8-f/16 range most of the time. If you are shooting portraits and people AND landscapes most of the time then the 24-70mm is more versatile. You have a crop body so you are sacrificing that wide angle no matter what....

If you had a full frame sensor then I would opt for the prime lenses of theirs because that is when I notice Canon really sings...

I use the 24-105mm on my 1ds3 mainly due to it's versatility. It tends to be the lens that lives on the body.

The only other thing I can add is this lens is optimized towards the wide end. If I need better performance at 70-105 I swap over to my 70-200 f2.8 L IS.

I use to think of this as a sharp zoom but now that i have shifted to 21mp, I would called the lens adequate for most uses.

I did own a 24-70mm f2.8 L and there wasn't much in it. Probably more down to sample variation.

If ultimate sharpness is your goal over versatility you would be better off with L series primes in this range.

i posted the same question here a while ago, in my case to be used on a 5dII.
in the end i went for the 24-70. here my personal reasons for this decision (your own may be different):

• weight and size of the lens doesn't matter that much to me. if light and compact is essential i use my g9. if i need quality i bite the bullet and am happy to carry the weight.
• in many situations where i use this type of zoom (reportage type work) i prefer working more at the wide end of the focal length range. sacrificing a bit at the long end doesn't hurt me as much as some other users.
• speaking of the wide end - less distortion on the 24-70 is important to me.
• the lens hood is much more efficient on this lens. i use it to shoot events and concerts among others and this is a big benefit with stage lighting.
• larger aperture means more to me than image stabilisation. typically, i get blur from subject movement before i'd get it from camera shake.
• slightly better, overall image quality.

as i said above, your own situation and needs may be different. i was torn for a long time between the two but so far haven't regretted my decision. i hardly use a dslr for 'walk-around' type shooting any more but am happy to use this as a standard lens for a larger, higher quality walk-around rig when required.
on shoots where i have to be mobile (above mentioned events etc.) i would typically pair it with a 85mm and/or 135mm prime and be ready for pretty much anything while still have a relatively compact kit bag.

but then, as somebody mentioned above, the 24-105 would probably be the better choice if you want a lens that you put on your camera and then want to be able to just use and forget about for the rest of the day.

I also have owned both, starting with the 24-105.

I found that after testing four copies of the 24-105 it was sharper than the best of four 24-70's on full frame. I seem to remember greater variation in the 24-105 copies than I've seen with other Canon lenses. The 24-105 began service as a travel & outdoor quiver-of-almost-one lens, but I struggled with the slow aperture so purchased the 24-70. After a couple years of owning both, I recently sold the 24-105 for 90% of original cost. I hate slow lenses, but do highly prefer the 70-200 f/4 over the f/2.8 version.

Pluses for the 24-70 are normal faster aperture, less distortion and yes the lens hood is most functional because the zoom extension is reverse from "normal".

Each use and opinion differs. have you considered buying a copy of both and giving them a try during your dealer's return period?

Alternately, and what I recommend to anyone considering buying lenses, how about renting them for a weekend? You can determine which one's general specs and handling fit your needs. Then buy the one you want and test to make sure it is mechanically and optically sound.

A number of people complain that some of the new lenses they buy are not actually "new, " someone else bought and returned it for whatever reason. This is my way of not contributing to this problem.

Paul

You can search for another thread on this topic; I own both lenses and use them on Eos-1Ds III and Eos-5D II bodies. I use the 24-70 f:2.8 a lot more, simply because most of my work is landscape shot from a tripod including a lot of stitched panoramics. The 24-70 in my experience is just a bit sharper, particularly in corners at the wider focal lengths. Because of the lens's zoom design, the hood is much deeper and more effective than the tiny shallow thing on the 24-105. Finally, the 24-105 vignettes badly at any aperture wider than about f:10. Even at narrower apertures it requires tedious work in Photoshop to damp down the corner vignetting enough to stitch any images with sky in them. At least for my work this is a huge shortcoming.

I do find the 24-105 most useful, as others have noted, as a 'walking around' lens mounted on one camera body slung around my neck. In that setting the IS is useful, and it's surprisingly sharp wide-open if you don't mind the vignetting. The extra millimeters at the long end are great for people shots. I always find myself wishing the 24-70 went a bit longer when I'm using it for portraits & candids, and I'm constantly swapping between the 24-70 and my 70-200 shooting landscapes. I always find myself wishing for something like a really sharp 28-135 or so; it would have to be a lot sharper than Canon's ancient original IS lens.