davidrb Loc: Half way there on the 45th Parallel

Depends upon your reasons for this post. IF you simply want to rid yourself of overlapping range then sell the 24-70. IF you realize these are two different lenses that are paid for, keep them both. You have already told us you rely on the opinions of others to make decisions then listen to what the voters say. Including big whites my 24-105 has given me more photographs than any other lens I own. Mine also shows a macro distance of 1.5'. Too versatile to part with.

Ruthlessrider

Thank you everyone.

MountainDave

I'll be a little contrarian here and advise selling them both and buying the 24-70 2.8L II which is way better than either of the f/4s. Buy a nice used one for around 1250., maybe less. Better resolution, better AF performance, better color. And it is built like a tank.

Longshadow Loc: Audubon, PA, United States

Interesting.
Reach is more important to me.

47greyfox Loc: on the edge of the Colorado front range

There was a time when I owned the Canon 24-70 f/2.8L ii and a 24-105 f/4L IS. Sitting along side was a 70-200 f/4L ii IS and the 100-400 f/4.5-5.6L. Hmm, redundancy…. Later, I bought a 1.4x iii TC from MPB and decided it was time to make a decision. I sold the 24-105 figuring (along with my 16-35 f/4L IS) that I was covered for just about any shooting scenario. But… occasionally, I wonder if I should’ve sold that 24-105, but it passes.

burkphoto Loc: High Point, NC

In your case, it's about reach. Personally, I would rather have speed. I would never buy a full frame f/4 lens shorter than 250mm. But faced with two f/4 lenses, one of which is slightly longer than the other, I'd trade the shorter of the two, even if it's not quite as sharp. I'd also consider trading both for the EF 24-70 f/2.8L II lens. Pairing that with the 70-200 f/2.8L II US ISM is the professional's choice, if you have the arm and wrist strength and budget to support it. That 70-200 f/2.8L is heavy!

All of that is a huge reason why I use Micro 4/3 now instead of Canon... My 12-35mm f/2.8, 35-100mm f/2.8, and 30mm f/2.8 macro give me everything I had in my Canon and Nikon days, albeit with two stops more depth of field and noise to deal with, much closer macro focus, and a lot less hit to the bank balance. None of those differences bother me.

delder Loc: Maryland

This sounds like a classic kit.

amfoto1 Loc: San Jose, Calif. USA

I disagree. The f/2.8 lens can't simply be called "better" and it's definitely not "way" better!

Sure, f/2.8 is a stop bigger so you have a little better ability to throw a background out of focus (though far less than an f/1.4 or f/1.2 prime lens offers).

BUT... There's no IS on the f/2.8 lens. The f/4 lenses can actually be better for low light shooting, with up to 4 stops of assistance from its IS.

Yeah, the f/2.8 is built like a tank. It's bigger and heavier than the 24-70mm f/4. Both are L-series, with similar build quality, sealing and durability.

Image quality simply isn't all that different. In fact, the 24-70mm f/4 very nearly matches the sharpness of the 24-70mm f/2.8 II. The f/4 lens' "worst" sharpness comparison is when wide open, around 50mm. You'll have a hard time seeing any difference in sharpness at other focal lengths. It often doesn't matter in images, but the f/2.8 lens has about a stop stronger vignetting than the f/4 lens. The two have similar flare performance at the wide end, but the f/4 lens is a bit more resistant at the 70mm end of the zoom range. And they have virtually identical distortion... minimal barrel at the wide end and pincushion at the tele end of the zoom.

The 24-70mm f/4 has MUCH closer focusing with its ability to shoot 0.70X magnification. That's more than triple the magnification possible with the 24-70mm f/2.8 II's 0.21X!

So, yeah... if you gotta have f/2.8, the EF 24-70mm f/2.8L USM II is "better". With it you also get a smidgen "better" image quality at some focal lengths and on some cameras slightly faster AF (cameras that can take full advantage of the larger aperture).

But if you want smaller and lighter with image stabilized low light capabilities, would like to leave your macro lens at home and want to save hundreds of $, well then EF 24-70mm f/4L IS USM would be "better".

imagemeister Loc: mid east Florida

No, no reason ....unless the weight of the 105 is burdensome .....

bonjac Loc: Santa Ynez, CA 93460

I don't know how easy this would be for you but, I did a sort of my photographs by lens and then for similar lenses compared the output of each lens and the focal length count. For me, it was quite informative and prompted me to do similar comparisons on other lenses. I learned alot from this with a couple of surprises and unanticipted realizations. Admittedly, it did take time but, as I said, I learned a lot.

Architect1776 Loc: In my mind

PS, the 24-70L f4 that the OP has is not the brightest Canon lens.
The 24-105 L II is very sharp except for the insane pixel peepers.
Need superb and hyper sharp reach? Then add the incredible 100-400mm L MII lens and get near macro included at no charge that the 70-200, either version, lack.

MountainDave

I used to own the 24-105 4L IS II and, in my experience, there is no comparison in any respect. I don't have time to dig out old reviews but here is the DxOmark sharpness grades:

On 5D IV:
24-70 f/4 18 (pretty good)
24-105 f/4 II 15 (not so hot)
24-70 2.8 II 21 (outstanding)

On 5DS R
24-70 f/4 21
24-105 f/4 II 14
24-70 2.8 II 32

Personally, I think AF performance is more important. The 24-70 has always been fast and accurate, among the best I've owned (a bunch.) It almost never misses. This includes a 77D I used to bring on hikes for lighter weight. The 24-105 was mediocre at best, especially at the long end. IMO, IS is a non-factor on 24-70. I didn't think 2.8 was very important until I bought one and discovered the creative benefit of a more shallow DOF. Rent one or buy a used one with a return privilege.

OldSchool-WI Loc: Brandon, Wisconsin 53919

___________________________(reply)

In reading some of the replies I have not seen any 'qualitative comparisons?" Isn't that the important question? I have roughly two dozen lenses and the fact is that single focal length lenses are sharper than zooms. Assuming your body has a 35mm sensor, why not take along a super fast 50mm, <F.2, a fast 100mm of F2.8 and if you need wide angle, a fast 28mm. Taking along the first two would possibly weigh less that your larger new zoom? Anyway, considering a heavy DSLR body, a case with a slot for the extra lens would not be a big thing. There are a few sharp zooms, but mostly in the 18-50mm lower level. And Sigma has a 50-150mm F2.8 EX HSM which costs variably used from $300 to $1000. which is pretty sharp. But think of the non-zooms and the fact that it is simply easier to create a top single focal lenth lens than a zoom which is nearly impossible to create a scale of sharpness over the range. Even after sixty years or more of zoom dominance.-----ew

Architect1776 Loc: In my mind

Why the obsession over "sharp"?
At normal viewing distance for any size enlargement most ALL current lenses, including zooms, are "sharper" than past generations of lenses.
Only those anally obsessed with pixel peeping over actual taking photos worry about sharpness today.
Yes, some lenses are sharper than others some zooms are sharper than many prime lenses.
The zoom allows much greater versatility and far quicker response time. No swapping lenses in adverse conditions, keeping the sensor cleaner. Greater composition flexibility that primes lack allowing concentration on the photo and not constantly swapping lenses. Or you left the prime that you needed because of space that a zoom would have covered.
Finally I have used the 24-105mm L with no complaints about "sharpness".

Longshadow Loc: Audubon, PA, United States

Definitely.