README: correct the documented cfg default

README.md

@@ -169,8 +169,8 @@ change can be judged without rerunning anything by hand.
 
 `--size` sets a square frame (or the frame *area* when `--image` supplies the aspect ratio);
 `--width`/`--height` override it and are floored to a multiple of 32. `--cfg` is `true_cfg_scale`
-and defaults to **1.0** — Qwen-Image-2.1 is meant to run without guidance, and `--negative` only
-takes effect above 1.
+and defaults to **1.5** with a default negative prompt. Stock Qwen-Image-2.1 runs without
+guidance (`--cfg 1`), which is still what `--cfg 1` and `negative_prompt=None` give you.
 
 Requirements: `torch`, `transformers`, `accelerate` and a `diffusers` built with Qwen-Image-2.1
 (`pip install git+https://github.com/huggingface/diffusers`) — the transformer subclasses