fix: remove pale background from negative prompt, disable by default

app.py

@@ -75,8 +75,9 @@ def load_pipeline():
 
 
 # Default negative prompt to avoid common issues
+# Note: Training data from CellaVision DM96/9600 has palid yellow background (desired)
 DEFAULT_NEGATIVE_PROMPT = (
-    "white background, pale background, washed out, overexposed, "
+    "white background, washed out, overexposed, "
     "low contrast, blurry, out of focus, multiple cells, overlapping cells, "
     "artifacts, noise, low quality, deformed"
 )
@@ -172,9 +173,9 @@ with gr.Blocks(css=custom_css, theme=gr.themes.Soft(primary_hue="red")) as demo:
                 gr.Markdown("---")
 
                 use_negative_checkbox = gr.Checkbox(
-                    value=True,
+                    value=False,
                     label="Use Negative Prompt",
-                    info="Enable to steer generation away from unwanted characteristics"
+                    info="Enable to steer generation away from unwanted characteristics (e.g., white backgrounds, blur)"
                 )
                 negative_prompt_box = gr.Textbox(
                     value=DEFAULT_NEGATIVE_PROMPT,