Weakness at 50mm:
I can not see any image of weakness at 50mm with my lens.
Focus shift:
A much discussed topic on the lens. This is or was a problem indeed, but was apparently released from Canon. I tested two lenses that had a more or less dominated focus shift. Ie. The farther one dims, the more the sharpness level is shifted relative to the focal point so that the focal point is no longer located in the center of the focus area. The actual focus point was the two lenses while still within the focal plane but depending on aperture the sharpness level has shifted so that the focal point was already in the edge region of the focal plane (tested course with tripod and unchanged manual focus, that it was merely dimmed) , I'm not a junkie test, when the displacement of the focus area would have been in a tolerance range, which is noticeable only in the laboratory but not in practice, it would have been no problem. The comparatively strong shift when stopping down but that was unacceptable. Therefore, these two lenses went by referring back to the error. After I read that the problem of Canon Fixed I have tested another lens. That no focus shift occurred more. Apparently no longer occurs in later productions on the issue. The error-free lens had the five-digit serial number 0300017XXX. The faulty lenses before had 4-digit serial numbers 0300003XXX. The problem seems to be so that history.
Conclusion: The lens is just a great standard zoom, which I the classic 24-105 L IS USM like to prefer, because it does not have the known weaknesses (distortion, mechanical weaknesses, fringing, only 8 diaphragm blades) and I to the area 70 may waive -105. In addition, image stabilizer is effective and the rudimentary Macro function is quite nice, though not comparable to a genuine macro-Glass. Because the focus shift problem was apparently solved, I give my new standard zoom really like 5 star.
