Hires denoise

How much the hires pass is allowed to repaint the upscaled image.

Typical 0.65

The second pass starts from the enlarged first image rather than from noise, and this decides how much of it survives. Low values keep the first pass's composition and mostly add sharpness; high values let the model add detail that was never there, and drift from the picture you were enlarging. It only reaches the request while the hires pass is on.
Size · Interactive explorer Hires denoise
The same picture rendered at 0.55Hires denoise 0.55 768 × 768
0.11

The useful band. This is the picture the first pass composed, drawn properly at the full size.

Fetching the example images.

Where the difference is

One setting against another, close up The same patch cut from both pictures, drawn one picture pixel to one screen pixel.
Compare against
A close-up patch of 0.1
0.1
A close-up patch of 1
1

0.1 · 276 × 276 1 · 276 × 276