Hires fix (high-resolution fix) is the SD workflow that generates a small image then upscales and re-renders it. Choose the right upscaler and denoise strength and quality jumps noticeably.
Three key parameters
| Parameter | Meaning | Recommended |
|---|---|---|
| Upscale ratio | Final size = base × ratio | 1.5×–2× |
| Upscaler | Interpolation / AI scaler | 4x-UltraSharp / Latent |
| Denoising strength | Degree of regeneration after upscale | 0.3–0.5 |
Upscaler comparison
- Latent — upscales in latent space, preserves style but occasional green blocks
- 4x-UltraSharp — strongest for realism, recommended default
- 4x-AnimeSharp — anime-specific
- ESRGAN_4x — general, stable
- R-ESRGAN 4x+ — best for photographic detail
Denoising strength
- 0.2–0.3 — preserves composition, sharpening only
- 0.4–0.5 — standard (recommended)
- 0.6+ — changes details, can "grow new things"
Gotchas
4× upscale crashes VRAM
1024 × 4 = 4096 is too big for most GPUs. Stick to 1.5×–2×.
High denoise grows new faces
0.7+ regenerates face details — sometimes a different person.