24-105L vs 24-70L

if I shoot at F4 on both lenses, would the IQ like sharpness and color rendition be the same (if shot under same shutter speed same iso)or would there be any differences?

No... Sharpness will be simlar but the 24-105 tends to have some pretty strong optical vignetting at some focal lengths and I think the color rendition/saturation of the 24-70 might be a little better.

But in general you'd have a pretty hard time telling apart 8x10s or 1x14s made from each lens (and the 28-135, for that matter).

Biggest difference... the 24-105 really struggles to shoot at f2.8.

You basically just need to decide between f/2.8 and IS... the rest is pretty much equal.

first of all, what are you shooting and what body will you pair it with?

I have 5D MK2 with 35L and sigma 85/1.4

I want to get a zoom lens for convenience but I really worry that the IQ will be disappointing coming from 35L and sigma 85/1.4

I would like to buy the 24-70L but it's really heavy. if there are no diff in IQ, I might as well buy 24-105L right?

If you think the 24-70 is heavy, wait till you do a prolonged session with a 70-200 2.8 on the camera.

Dr.TC wrote in post #12499167
I have 5D MK2 with 35L and sigma 85/1.4

I want to get a zoom lens for convenience but I really worry that the IQ will be disappointing coming from 35L and sigma 85/1.4

Dr.TC wrote in post #12499176
I would like to buy the 24-70L but it's really heavy. if there are no diff in IQ, I might as well buy 24-105L right?

Trust me on this. You ain't missing out much if you have the 35L and the Sig 85mm. You definitely don't get the bokeh quality/separation with the 24-70L like you do with the 35L and that's just due to the aperture. And of course, you also don't get the color, and sharpness.

The 35L is a great lens for a walk around and I'd much rather use that lens over the 24-70. Have you considered adding another prime to your collection? like the 24L, 50L or the 135L?

Marloon wrote in post #12499064
first of all, what are you shooting and what body will you pair it with?

That sounded like an EF-S 17-55mm IS trap, lol.

OP, both lenses are about the same at f/4, but the 24-70 has a slight edge at the extreme edges and vignetting over the the 24-105.

I've got 24L, 35L and 85L. The 24-105 is flat out a nice, all around lens. Perfect fit on a 5DII. I think you've got your speed covered with you primes.

Vignetting is easily corrected if you don't like it, and IS makes up for the difference in light over the 24-70.

Dr.TC wrote in post #12498930
if I shoot at F4 on both lenses, would the IQ like sharpness and color rendition be the same (if shot under same shutter speed same iso)or would there be any differences?

The biggest difference @f4 is that the 24-105 has horrible distortion at the wide end, nasty vignetting, worse bokeh.
The only advantages of the 24-105 is the IS, the extra 35mm at the long end, and little less weight.

I'd pick the 24-70 anytime. YMMV.

24-105, more versatile of a lens, IMO. Yes, 2.8 lets in more light, but still not enough for low light, indoor shooting. At that point you'd use a prime or flash anyway, so 2.8 isn't that advantageous. The 24-105 is a great walk around lens: lighter weight, IS, more range, costs less.

The 24-105's strengths outweigh its weaknesses. If I pixel peep I can see better IQ with my 28-70 f/2.8L, but the 24-105 gets a lot more use.

I have both the 24-105 and the 24-70 and agree with Tapeman that the 24-105 wins in the weight and usefullness category. It is my walk around lens. The 24-70 comes out when my pics have to be the best they can.