I received a Nikon 24-70 mm f/2.8 Nikkor S the other day, and wasted no time in clipping it into a Z7 and getting started on testing. The lens has received a lot of attention, and many are saying it’s the best of the 24-70/2.8s.
The first thing I did was check to make sure I have a good copy, using this test. Target distance was 38 meters. Testing note: Nikon still has not fixed the atrocious laggy focus-by-wire algorithm they are using in the Z6 and Z7. It was a huge PITA to focus for these shots. I developed all the images in this post in Lightroom, with Adobe Color profile, and sharpening amount 20, radius 1, and detail 0. This is quite a bit less sharpening than the Adobe default.
At the shortest focal length (and wide open, as are the following two sets), the center is very crisp. A fair amount of light falloff in the corners and on the short sides is visible, but it appears to be a bit better than the run-of-the-mill 24-70. The lens has higher resolution for features perpendicular to radial lines in the focal plane than for features parallel to those lines.
At a focal length of 35 mm, the center still looks quite crisp. The corners and edges are not as sharp, though they are roughly symmetrical, indicating a good copy. From the test results further down the page, it is apparent that the reason for the corner softness is file curvature, not simply resolving power.
The center isn’t as sharp at 70 mm. The field curvature appears to be a little better. This loks like a good copy of the lens.
For my next test, I moved the target closer, to 14 meters, and made an aperture series in the center and in the upper right corner. I used AF-S with pinpoint in the center, but I couldn’t get pinpoint to work in the corner, so I switched to the small spot. I focused for each shot, eliminating field curvature from the equation. I made 3 shots at each test condition, and picked the sharpest.
In the center, at 100% magnification:
The three columns are, left to right, 24 mm, 35 mm, and 70 mm. The five rows are, top to bottom, F/2.8, f/4, f/5.6, f/8, and f/11. F/4 is the sharpest aperture at all the focal lengths. Diffraction essentially eliminates aliasing at f/11 at all focal lengths. The 70 mm sharpness looks better than with the screening tests. I’m tentatively putting this down to missed focus because of the lousy focus-by-wire software. I did make three shots at each location and took the best, but maybe I should have make six or eight. Oh, wait, that would mean that I’d have to subject myself to more manual focusing. Nah…
In the corner:
The three columns are, left to right, 70 mm, 35 mm, and 24 mm. Sorry about that. I’d say that the best aperture for all three focal lengths is f/5.6. The 70 mm corners are indeed much sharper than in the first test.
So far, this is quite encouraging.