Why photo models struggle
Photo-trained upscalers expect texture everywhere: skin pores, grass, noise. Give them a cel-shaded frame and they’ll add soft mottling to flat colour and turn line ends into brush strokes. Creative diffusion upscalers go further and re-imagine shading. That’s sometimes nice for illustrations, but rarely faithful to the artist.
Models that suit drawn images
| Model family | Good at | Notes |
|---|---|---|
| Real-ESRGAN anime (x4plus_anime_6B) | Anime stills, illustrations | Small, fast model in the open-source Real-ESRGAN project; also used in desktop apps such as Upscayl |
| realesr-animevideov3 | Anime video frames | A lighter Real-ESRGAN model aimed at video |
| waifu2x and successors | Line art, denoising JPEG anime art | Long-running open-source project with denoise levels |
| Anime4K | Real-time playback upscaling | Open-source GLSL shaders for video players, not for offline masters |
Settings that matter
- Denoise level: raise it for screenshots of streamed video or saved JPEGs; keep it low for clean digital art, which would otherwise lose fine hatching.
- Scale: 2× is often enough for wallpapers; 4× for print. Re-running 2× twice usually looks worse than a single 4×.
- No extra sharpening afterwards. Anime models already produce hard edges.
Manga and black-and-white scans
Screentone, the dot patterns used for grey shading, is the hard part. Upscalers either blur it to grey or turn it into irregular noise. For faithful results, scan at a high ppi and keep the tone as it is. For reading on a screen, a model with denoising that smooths tone into flat grey is often more pleasant. Choose deliberately, and compare the two at 100% with the A/B tool.
Pixel art is a special case
Pixel art is meant to show its pixels. Scale it by whole numbers only (2×, 3×, 4×) with nearest-neighbour interpolation, so each pixel becomes a crisp block. Non-integer factors (2.5×) make some pixels wider than others. AI upscalers and bilinear or bicubic filters smear the edges. If you want smoothed edges, use pixel-art filters such as hqx or xBR, which were designed for exactly this.
FAQ
What is the best upscaler for anime?
Use models trained on anime and line art: Real-ESRGAN’s anime models (RealESRGAN_x4plus_anime_6B for stills, realesr-animevideov3 for video frames), waifu2x and its successors, or anime presets in desktop apps. General photo models and creative diffusion upscalers tend to add texture to flat colour.
How do I upscale pixel art?
Don’t use AI at all for authentic pixel art. Scale by a whole number (2×, 3×, 4×) with nearest-neighbour, which keeps every pixel a crisp square. Pixel-art-specific filters such as hqx or xBR smooth the edges in a controlled way if you want that look.
Why do my upscaled anime screenshots have halos?
Ringing or halos around lines usually come from over-sharpening, or from JPEG artefacts in the source being enhanced. Use a model that also removes compression artefacts, and avoid extra sharpening afterwards.