E621 has tag group:aspect ratio tags for lots of nicely rounded numbers and common screen sizes. But there is one prominent aspect aspect ratio missing, which is the aspect ratio of ISO paper sizes - sqrt(2):1 i.e. 1.414...:1. In case you don't know, ISO paper sizes have an unique property, that when folded or cut in half, the halves also have the same aspect ratio (on paper; in practice there can be 2 mm tolerances.)

Naturally, artwork intended for print using ISO paper has this aspect ratio, including plenty of doujinshi pages. This makes me think e621 should have automatic tags for this aspect ratio, both landscape and portrait.

There is an obvious problem to implementing this - sqrt(2) is not a rational number. The existing aspect ratio tags are all for exact ratios, but images in the size of ISO paper typically have aspect ratios that are only close to 1.414 (some can deviate to as far as 1.422) so the automatic tagging will need to check the aspect ratio using a range, which needs to be decided on.

What do you think?

I'd argue this is more useful than some of the existing aspect ratio tags, since it's actually widely used and with good reason.

Although, note that you can also use the ratio metatag: ratio:1.414 / ratio:0.7072

I'm pretty sure last time aspect ratios were discussed, the decision was along the lines if we're tagging these, we should tag all of them so there's no subjective cutoff points, but keep them whole numbers only.
Which is completely unhelpful and unnecessary and leaves out stuff like this completely.

would there be any problem just calling the tags 1:sqrt2 and sqrt2:1? or just forgoing numbers entirely and calling it like iso_ratio_(portrait) and iso_ratio_(landscape)? I know it breaks the naming convention a bit, but it'd be better than just not having proper tags at all.

sipothac said:
would there be any problem just calling the tags 1:sqrt2 and sqrt2:1? or just forgoing numbers entirely and calling it like iso_ratio_(portrait) and iso_ratio_(landscape)? I know it breaks the naming convention a bit, but it'd be better than just not having proper tags at all.

I object on the grounds that nobody knows what those mean off the top of their head

strikerman said:
I object on the grounds that nobody knows what those mean off the top of their head

no one knows what 64:35* means of the top of their head either.

_{*intentionally not a tag wiki link. 'have to guess if those are just two random two-digit numbers I picked or an actual canon, populated tag.}

sipothac said:
64:35

Aspect ratio tags were a mess until just now. I've just cleaned them up, and that one has been cleared out. We don't need to create aspect ratio tags to create aspect ratio tags. I completely disagree with making these tags.

(In case you haven't noticed, tag_group:aspect_ratios went from over 700 tags to under 30. There has been a growing issue of nonsensical aspect ratio tags which has finally been dealt with.)