HappyOnigiri-ComfyUI-Meld/docs/en/nodes/MeldAutoExposure.md

Meld Auto Exposure (MeldAutoExposure)

A node that analyzes image brightness (luminance) and automatically applies gamma correction to approach a target brightness level. It is useful for brightening generated images that are too dark, or conversely, toning down images that are too bright.

Connection Image: KSampler -> VAE Decode -> [Meld Auto Exposure] -> Save Image

Input

Required

Name	Type	Default	Description
image	IMAGE	-	The input image to correct. Supports batch input, where each image is analyzed and corrected individually.
correction_strength	FLOAT	0.5	Correction Strength (0.0 - 5.0). Higher values apply stronger force to reach the target brightness. At 0.0, no correction is applied (gamma 1.0). Start around 0.5 and increase if the effect is too weak.
target_brightness	FLOAT	0.5	Target Brightness (0.1 - 0.9). 0.5 is medium brightness. Increase (e.g., 0.7) for brighter results, or decrease (e.g., 0.3) for darker results.

Optional

Name	Type	Default	Description
gamma_limit_min	FLOAT	0.2	Minimum gamma limit. Prevents the image from being corrected to be extremely dark.
gamma_limit_max	FLOAT	2.5	Maximum gamma limit. Prevents the image from being corrected to be extremely washed out (white).

Output

Name	Type	Description
image	IMAGE	The brightness-corrected image.
calculated_gamma	FLOAT	The actual applied gamma value (calculated). Returns the average for batch inputs.
current_brightness	FLOAT	The average luminance of the original image. Returns the average for batch inputs.

Tips & Mechanism

• Auto-Adjustment Logic: Calculates the average luminance (Rec.601) of the image and derives a gamma value based on the difference from target_brightness.

  • If the original is darker than target → Corrects to be brighter.
  • If the original is brighter than target → Corrects to be darker.

• Tuning Tips:

  • First, set target_brightness to your preferred brightness level.
  • If the correction causes quality degradation (e.g., contrast is too harsh), lower the correction_strength.
  • Conversely, if the correction is insufficient, increase correction_strength or widen the limiter range (gamma_limit_min/max).