You replied to a thread about a photography website. I don't think 720p images are the norm for that use case.

In any event, I don't think the AVIF result at 250 KB is acceptable for photography either: https://0x0.st/o93a.avif - There's a ton of smearing and blurring that's very obvious when you're viewing the image at full size.

3000x2000 basically means "fullscreen on a retina display @ full resolution". You can only reasonably show one picture like that at a time. So it's completely OK to have the currently displayed picture at that resolution/size.

But all photo should be loaded at a much lower size, initially, and only downloaded at full size the the user puts them in full screen.

I know lazy loading is in vogue, but as a user it only ever seems to create problems for me. I’d much rather the website download all the images ahead of time on page load, so I don’t have to wait for full quality versions each time I full screen a different image.

This is the restaurant equivalent of : "We are at an all you can eat buffet, let me take 10 plates even if I only realistically will eat 4, so that if I want any more I don't have to stand up again".

While the other way (loading each image as you view them, or lazy) is functionally equivalent to waiting in line for each separate dish, which isn't quite so fun.

Maybe gallery sites could consider offering a preference to load all images upfront if you intend to view them all.

A good example would be housing sites, where viewing higher quality photos of each listing is a primary use case.