Unfortunately, whenever someone mentions that Lena was a nude model (perhaps to suggest objecting to the image's use in academic settings as an appropriate testbed), everyone gets angry. Negative reinforcement, I suppose.

That negative reinforcement yields good results though.

To clarify: the only meaning "good results" could refer to is the continued use of a cropped piece of pornography as a standard test image for image research for over twenty years.

Oh, but aren't all SFW pictures cropped pieces of pornography at the end of the day?

If you expand the field of view enough eventually there's going to be people having sex in it.

Not necessarily. If the camera and primary subject are in an enclosed room, all you're ever going to get is more wall.

Of course not, and its really worrisome that you think that. Most of the set of grey scale 50x50 pixel images are not crops by the simple fact that they contain no correlations at all, that's simple combinatorics.

Is that actually already pornography?

Well, from context its pretty clear it is intended to be used as pornography and I think that's good enough to label it as such.

I just meant, that western society seems to have become more accepting since the photo was shot, and these days people might classify it as an 'artsy nude' instead?

Which is why I think it would be really interesting to run a set of Robert Mapplethorpe's photos on it to see how they are classified. Some of his photographs are much more explicit while at the same time are much more specifically art. He photographed a lot of posed homoerotic BDSM Large Format photos specifically staged to develop tension, but not necessarily or even usually sexual tension or disgust tension, between the viewer and the person posed in the photo as a person and as a form. Alternatively he photographed large format calla lilies or orchids that are explicitly erotic. The photos were almost always black and white, and were s seen as controversial when he was alive and then again right when he died.

Then, in contrast, run some Japanese woodblocks in the Ukiyo-e style, since many of those are actually explicit. (including straight up porn woodblocks) Most Japanese woodblocks are also highly stylized as well, and it can take a moment to realize what is going on, including in some of the pornographic or hinting at the explict/could be explict/explict personalities.

I'm not going to say all Robert Mapplethorpes are safe for all work environments, nor all Japanese woodblocks, but I am curious to know if it can see the difference of person in homoerotic outfit who looks physical and gets you to notice his form, vs a Suzuki Harunobu being a bit more sly but more more explict in he is telling a story and his story is sex

I don't think you can take something which was once meant to be erotic pornography and add time to make it an 'artsy nude.' But if you can point to an example from the history of art, that would make your claim more reasonable.

I've always thought that was part of the joke.