After a long period of hibernation I finally had time to write a review and this being an important issue as my main workhorse and landscape lens would be in the 24-70mm range. For a long period of time I had wanted to get a reasonably sharp lens for this range and I owned two copies of the 24-70mm f 2.8 MK 2, unfortunately both these lenses were not outstandingly better than the f4 lenses.
Rather than flood the page with cropped photos, my impression is given below.
Price performance, the 24-105mm f4 IS comes on top as it has the best range (24-105mm) best price (around $800 AUD) and is not far behind the other two in image quality. In fact the best all rounder I think.
The 24-70mm is f4 is the most compact out of the three lenses and has the best corner sharpness out of the three lenses at the lower end (24-35mm) as shown in fig 4,5,6. (below). Although it has a phenomenon called lens creep the price has come down from AU$ 1,500 to AUD 1,000 and has macro capabilities as well. This makes it a good contender as it has the best image stabilization capabilities as well.
Center sharpness is almost the same in all lenses at the lower end but the 2.8f mk2 has a distinctive edge over the other two. (Fig 1,2,3) In the higher range (50mm) the 2.8f mk2 is surges ahead and is sharper than the rest making it an ideal portrait and wedding photography lens. The downside being the size, weight, price and lack of image stabilization, which are significant negatives for this lens.
Vignetting is found in all three lenses at the lower end (24mm) but the worst culprit is the 24-70mm f4 IS lens.
The parameters used for this comparison are given below
Camera used : Canon 5d MK 3
Shutter speed was 1/100 sec
AV mode with aperture set at 8
ISO speed 100 and on AWB mode.
A tripod was used with 2sec timer on camera.
All photos were cropped at 100%
Comparison at 24mm at the CENTER
(Fig 1) -24-70mm 2.8f MK2 1
(Fig 2) -24mm 24-70 f4IS
24mm at the CORNER Comparison
(Fig4) 24mm 24-70 f2.8 MK2
(Fig5) 24mm 24-70 f4IS
(Fig 6) 24MM 24-105MF4 IS