ComfyUI Node: Sigmoid Correction

Sigmoid Correction:

The SigmoidCorrection node is a powerful tool in image processing that applies a sigmoid function to adjust the contrast of images. This node is particularly useful for enhancing the visual quality of images by modifying the intensity values in a non-linear fashion. The sigmoid function is known for its S-shaped curve, which can effectively compress or expand the range of pixel values, thereby enhancing the contrast in specific regions of an image. This method is beneficial for highlighting details in images that might otherwise be lost in shadows or highlights. By adjusting the cutoff and gain parameters, you can control the midpoint and steepness of the sigmoid curve, allowing for precise control over the contrast enhancement process. This node is ideal for artists and designers looking to improve the visual impact of their images without delving into complex technical adjustments.

Sigmoid Correction Input Parameters:

images

This parameter represents the input image(s) that you want to process. The node will apply the sigmoid correction to these images, enhancing their contrast based on the specified cutoff and gain values.

cutoff

The cutoff parameter determines the midpoint of the sigmoid function. It controls the point at which the input values are centered, effectively setting the threshold for contrast adjustment. The default value is 0.5, with a minimum of 0.0 and a maximum of 1.0. Adjusting this value shifts the sigmoid curve along the intensity axis, allowing you to target specific tonal ranges for enhancement.

gain

The gain parameter controls the steepness of the sigmoid curve, affecting how quickly the transition occurs around the cutoff point. A higher gain value results in a steeper curve, leading to more pronounced contrast changes. The default value is 5.0, with a minimum of 1.0 and a maximum of 10.0. By fine-tuning the gain, you can enhance subtle details or create more dramatic contrast effects in your images.

Sigmoid Correction Output Parameters:

images

The output is the processed image(s) with enhanced contrast. The sigmoid correction modifies the intensity values based on the specified cutoff and gain, resulting in images that have improved visual clarity and detail. This output can be used directly in your projects or further processed with other nodes for additional effects.

Sigmoid Correction Usage Tips:

• Experiment with different cutoff values to target specific tonal ranges in your images, such as shadows or highlights, for more focused contrast enhancement.
• Use higher gain values to create more dramatic contrast effects, but be cautious of over-enhancing, which can lead to loss of detail in certain areas.
• Combine SigmoidCorrection with other image processing nodes to achieve a balanced and visually appealing result.

Sigmoid Correction Common Errors and Solutions:

"Invalid image input"

• Explanation: This error occurs when the input provided is not a valid image format or is corrupted.
• Solution: Ensure that the input is a valid image file and is not corrupted. Check the file format and try reloading the image.

"Cutoff value out of range"

• Explanation: The cutoff value provided is outside the acceptable range of 0.0 to 1.0.
• Solution: Adjust the cutoff value to be within the specified range. Use values between 0.0 and 1.0 for optimal results.

"Gain value out of range"

• Explanation: The gain value provided is outside the acceptable range of 1.0 to 10.0.
• Solution: Adjust the gain value to be within the specified range. Use values between 1.0 and 10.0 to ensure proper contrast enhancement.