That was the first example I ran across. I’ve seen others. Focus shift is independent of the design age of a lens. In practice, it’s probably not a huge issue with the 50L because the typical subject distance for that lens is great enough to obviate the issue.
The magnitude of focus shift is inversely proportional to subject distance, and the RF 100L is a macro lens. If you’re using it for portraits, you likely won’t be affected by the focus shift. If you’re stopped down to f/14 for macro, also little to no effect. But with macro subjects at middle apertures, I suspect it will be noticeable with subjects like insects, where sharp focus on the eyes (or nearest eye) is critical, and focus shift would put the focal plane behind the eye.
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