Comfy-Org / Comfy-Org/ComfyUI_frontend

🐛 Bug: Output image turns completely gray when denoise is too low

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area:previews verified bug
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Description

When running the generation script, setting the denoise value too low (e.g., 0.1 or below) in the KSampler node causes the generated image to appear completely gray or blank.

Steps to Reproduce:

Open main.py or the workflow JSON

Set "denoise" to 0.1 in the KSampler node

Run the script and check the output image

Expected Result:
The image should still contain visual content with slightly less noise.

Actual Result:
The output image is fully gray with no visible structure or content.

Possible Cause:
Low denoise values suppress the diffusion process too early, preventing the model from adding any meaningful detail to the latent image.

Suggested Fix:
Set denoise to at least 0.5 or higher for usable results. The default of 1.0 is generally safe unless fine-tuning style transfer or img2img.

References:

[ComfyUI docs](https://github.com/comfyanonymous/ComfyUI/wiki)

Hugging Face forum discussion on denoise thresholds

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-4232-Bug-Output-image-turns-completely-gray-when-denoise-is-too-low-2196d73d365081d1a454d4e8831afdb4) by [Unito](https://www.unito.io)

Contributor guide

Open the contributing guide

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