Here is a head to head comparison of the Nikon 18-35mm f/3.5-4.5D ED-IF AF, 18-70mm f/3.5-4.5G ED-IF AF-S DX and 24mm f2.8 AF prime lenses.
The D70 camera settings were:
JPG-Fine, aperture priority, Exposure Comp +1.0EV, ISO 200, WB Cloudy, AF-S, all images auto-focus, color mode Ia, Tone comp: Normal, Hue adjustment: 0 deg, Saturation: normal, sharpening: normal, shutter speed between 1/20th and 10 seconds depending on aperture. The tripod is a Bogen 3051 with a heavy pan/tilt head – a beast.
The 24mm was done first, then the 18-35mm then the 18-70mm were set to 24mm. I made sure the zoom lenses were at 24mm by shooting and adjusting the lens until the camera LCD indicated the lenses were shooting at 24mm. The light was becoming progressively more blue and only 2 minutes passed between lens tests. The test was done after the wall was in the shade. I used the histogram to try and make the exposures relatively equal. The 18-70mm required an higher exposure compensation of EV +1.3 because I’ve found my lens is off by -0.3EV.
f-stop 24mm f2.8 AF 18-35mm f/3.5-4.5D ED-IF AF 18-70mm f/3.5-4.5G ED-IF AF-S DX
f 2.8 N/A N/A
f 4 (18-35 was at f4.2)
f 25 N/A N/A
Sample images removed for website update
24mm Sharpness data
Using the JPG file size as an indicator of sharpness, several series of shots were taken with the 24mm f2.8 lens on a heavy Bogen 3051 tripod with matching pan-tilt head. The favorite subject, a brick wall, was used to conduct these tests. Between every series, the camera was refocused using autofocus. The camera body was made parallel to the wall to help eliminate depth of field reductions in the sharpness measurement.
From graph 1, it can be seen that my particular 24mm Nikon lens sample performs best at f11. These numbers cannot be compared against other lenses, as I do not have a baseline standard for comparison. This graph only provide information about the sharpness of my Nikon 24mm lens sample at various apertures. Lens sharpness rolls off at f16 and f22 due to diffraction, as expected.
Nikon 24mm f2.8 focus speed
Based on JPG file size, the samples showed the most sharpness at f5.6 on all files. There is a marked decrease in image sharpness from f16 to f22 on each lens, as is expected when the lens becomes diffraction limited. Surprisingly, each lens looks really good as soon as they are stopped down one stop from open. If you would like to see the lens aperture affect in a progressive way, download each of the images above, put them into a folder and quickly flip through viewing them in Window Fax/Image viewer or Mac iPhoto. Using the flip-book technique is how I did my initial assessment of how each lens was performing.