>>1934720I'll have you know that most Japanese digital artist have no clue about image quality, Loads of uploads on pixiv, where most of them upload free stuff, are badly compressed, not anti-alliased etc.
If you want really high quality, you're better of looking for scans of original works, seeing as most "pro" artists do not upload their work to the public web, not in full quality anyway.
Hentai/Manga scans can be found on sadpanda and range from normal to high quality.
Individually scanned pages from artbooks can be found on minitokyo and are ridiculously high quality(like pic attached).
Private torrent sites like AB and BBT host fully scanned artbooks, and these range from normal to high quality.
If you want digital, you're best of using Pixiv Dowloader, some of the boorus and reverse image searchers like sauceNAO and IQDB.
