Specific modern technical issues with the original scan are:
Lena contains about 250,000 pixels, some 32 times smaller than a picture snapped with an iPhone 6. And then there’s a quality problem: The most commonly used version of the image is a scan of a printed page. The printing process doesn’t produce a continuous image, but rather a series of dots that trick your eye into seeing continuous tones and colors. Those dots, Acton says, mean that the scanned Lena image isn’t comparable to photos produced by modern digital cameras.
[..] Scott Acton, the current editor of IEEE Transactions [..] and two former editors revived the old call for a ban, and proposed to the journal’s editorial board that IEEE Transactions institute a moratorium on Lena research. “In 2016,” he says, “demonstrating that something works on Lena isn’t really demonstrating that the technology works.”
the implication being that too many algorithms were trained on the Lenna image, to the point where the ASCII phrase LENA.JPG can now be expanded to the full original uncompressed image.
It, along with the Mandrill image, are quaint historic footnotes examples of types of images (drum scanned from magazine prints) that are no longer anything close to mainstream examples suitable for reference.
> it's surprisingly hard to find a good alternative test image.
https://arxiv.org/pdf/1202.6429v3.pdf
uses a licenced image of Italian heartthrob Fabio Lanzoni with skin tones and fine detailed blond hair.