Scheduler
How the noise is removed over the steps: big steps first, small ones at the end, or evenly.
In plain words
The scheduler decides how much noise is left after each step. Picture a staircase from "all noise" down to "no noise": the scheduler sets the height of each stair. Most schedulers take big stairs at the start (where the composition forms) and small ones at the end (where fine detail forms). The list of noise levels is called the sigmas.
Where you meet it in a graph
- The
schedulerfield of KSampler and KSampler (Advanced). - BasicScheduler, KarrasScheduler, BetaSamplingScheduler and similar nodes give
SIGMASto SamplerCustom or SamplerCustomAdvanced. - ModelSamplingSD3, ModelSamplingFlux and ModelSamplingAuraFlow change the model's own noise curve with a
shiftvalue. Wan graphs use ModelSamplingSD3 withshift5 to 8: a higher shift spends more steps at high noise, which helps large layout and motion. The node's name is historical; Wan uses it too.
Values in practice
| Name | Typical use |
|---|---|
normal | The default; fine for most models. |
simple | The default of many Flux, Wan, Qwen-Image templates. |
karras | With dpmpp_2m and SDE samplers on SD 1.5 and SDXL; good detail at 20 to 30 steps. |
exponential, sgm_uniform | Specific models and turbo or lightning versions ask for them. |
beta, linear_quadratic, kl_optimal, ddim_uniform | Newer or special cases; use when a template names them. |
Typical mistakes
- Changing the scheduler of a distilled or turbo model: these are trained for one schedule (often
simpleorsgm_uniform); others give blur or noise. - Forgetting shift on Wan: sluggish motion, detail that falls apart.
How the app helps
The video lessons check shift between 5 and 8 on both ModelSamplingSD3 nodes. The node descriptions explain SIGMAS and BasicScheduler, and Choosing a sampler and a scheduler compares schedulers on one seed. In Properties, a field with a built-in note has a button What this field does next to its name; it opens the note under the field: what the field does and what to put in it.