There is endless debate as to which is the best Nikkor Z zoom lens at 400 mm focal length. I have all three of the lenses in question: 180-600 mm f/5.6-6.3 VR; 100-400 mm f/4.5-5.6 VR S; 28-400 mm f/4-f/8 VR. On the Z50ii I could see little difference between them in the real world in terms of sharpness but last week in an idle moment I thought I would compare the three on a real scene at 400 mm (600 mm in full-frame terms) looking only at sharpness (that mix of resolution or acuity and contrast).
I aimed my camera at the local school (50 m away) on a quiet Sunday morning. There was no sun and a slight breeze—ideal conditions for avoiding thermal gradients in the air between camera and target. I compared out-of-camera jpgs (which have of course been processed to that stage) at constant aperture (f/8 the maximum of the 28-400), and base ISO (100). The shutter speed (on aperture priority mode) remained at 1/100 sec. VR was off and I chose a shutter delay of 2 sec to avoid vibration from any movement of the floor the tripod was standing on. I had to change the mounting for the lenses (28-400 has no collar) in use but made the changes as quickly as possible and each time I made sure the centre autofocus point (AF-S) was as near I could get it on the same object—a child’s cut-out drawing—on the inside of the school window.
With the images cropped to the same size in Lightroom I really could not see any material difference in sharpness at the centre of the frame. I then moved the crop to the bottom edge of the frame where the plane of focus was virtually identical. There was a slight difference in sharpness in the order one would expect from the price of these lenses (100-400 mm f/4.5-5.6 VR S > 180-600 mm f/5.6-6.3 VR > 28-400 mm f/4-f/8 VR) but it was slight.
A DX camera body used with these lenses offers more than the increase in effective focal length—from 400 to 600 mm in this case. These are FX (full-frame) lenses and any only the centre of the image is used. In lenses where resolution drops from the centre outwards, the edge definition of DX-camera image is higher than one taken by an FX camera, as was evident when I used my Z8 for the same series of shots.
What struck me was that although the pixel peepers seem to think they will get a better image with, say, the most expensive of these three lenses, there was very little difference in actual sharpness between the three at the one focal length of 400 mm (600 mm equivalent) in the centre of the field.
It is a pity that the MTF charts published by Nikon only contain data from either end of the focasl length range and at a range of apertures up to the point at which resolution becomes affected by diffraction in the various Z cameras. The charts are nowadays theoretical but designers now have such sophisticated software that they know the photographer's reaction to a particular lens before the first one is even manufactured. Good performance charts would save a lot of user testing and endless debate.
I shall continue to use my Z50ii-28-400 mm combination for general overseas wildlife watching trips (we avoid ‘photographic’ tours like the plague). That combination has produced published photographs—with help from RAW images and Lightroom Denoise, and with ISOs from 100 to 52,000—with everything I have pointed it at from hummingbirds to humpback whales. For other sorts of trip one of the other two zooms is a better choice.
Compression for Blogger may affect how the photograph below appears.
