When I saw the introductory photos taken with the Sony a7RM3 outfitted with the new 24-105 F:4 G OSS I was very impressed and felt it was time for me to change from my Nikon D800 to the Sony mirror-less system.I purchased an a7RM3 withthe new 24-105 G, the 100-400 F:4.5 GM and the 16-35 F:2.8 GM.This combination provides a nice overall system with a nice walk around lens.
I proceeded to run some quality tests on the system with all of the lenses and have found a problem with the 24-105.I photographed an old lens test chart that I had put together in my film days.It uses the NBS 1952 lens resolution charts.The charts are placed in the center and corners of the frame.
The 100-400 GM and the 16-35 GM both tested very well with 80 lines/mm everywhere in the frame, center and corners.I tested the lenses at min, max and central focal lengths.
The 24-105 G, however, is quite different.It tested very well with 80 lines/mm across the frame at min and max focal lengths, I was quite delighted.When I went to 60mm the results were not good at all and when I tried stopping down to F:8 the results were even worse.The problem I see is that the left side of the frame is very soft while the center and right side test okay.The NBS test charts have a thin lined circle in the center and that thin line becomes doubled when it is tangent to a radius drawn from the frames center.I returned the lens to B&H and they replaced it with another new one.The second lens exhibits the same problem.Since my other two lenses test okay, and the 24-105 tests okay at min and max focal lengths I feel quite certain that the problem is with the 2 lenses tested and not the camera body.
I am beginning to wonder if I just got units from a bad run or if there is a mechanical design error in the zoom rails causing misalignment.I realize that for a great many photos this is not too great a problem, but when photographing flat surfaces it does show up.When I shot a brick wall, left side softness was quite apparent in the mortar and brick texture.I am thinking seriously of sending the second lens back and getting the 24-70 F:2.8 GM even though it is very heavy and does not have OSS.
Has any one on the Forum seen a similar problem?