ComfyUI Node: ◎ Radiance HDR Exposure Blend

◎ Radiance HDR Exposure Blend:

The HDRExposureBlend node is designed to enhance the dynamic range of images by blending multiple exposures, a technique commonly known as exposure bracketing. This process involves combining highlights from low exposure images and shadows from high exposure images to achieve optimal color grading and detail preservation across the entire tonal range. The node supports various blending methods, such as Mertens Fusion, Luminance Weighted, and Laplacian Pyramid, each offering unique advantages for different scenarios. By leveraging these methods, the node allows you to create images with rich details in both bright and dark areas, making it an invaluable tool for photographers and digital artists aiming to produce high-quality HDR images.

◎ Radiance HDR Exposure Blend Input Parameters:

low_exposure

This parameter accepts a tensor representing the low exposure image. It is crucial for capturing highlight details, which are then preserved in the final blended image. The low exposure image is typically darker, ensuring that bright areas are not overexposed.

high_exposure

This parameter accepts a tensor representing the high exposure image. It is essential for capturing shadow details, which are then preserved in the final blended image. The high exposure image is typically brighter, ensuring that dark areas are not underexposed.

blend_method

This string parameter determines the blending technique used to combine the exposures. Options include "Mertens Fusion," "Luminance Weighted," "Shadow/Highlight Mask," and "Exposure Weighted." Each method offers different advantages, such as natural-looking results or enhanced contrast.

mid_exposure

An optional tensor parameter for a middle exposure image. When provided, it is normalized to the same exposure scale as the low and high exposures, offering additional detail and balance in the final image.

shadow_weight

A float parameter that influences the weight given to shadows during blending. It ranges from 0.0 to 2.0, with a default value of 1.0. Adjusting this can enhance or reduce shadow prominence in the final image.

highlight_weight

A float parameter that influences the weight given to highlights during blending. It ranges from 0.0 to 2.0, with a default value of 1.0. Adjusting this can enhance or reduce highlight prominence in the final image.

transition_smoothness

A float parameter that controls the smoothness of the transition between different exposure areas. It ranges from 0.05 to 1.0, with a default value of 0.3. A smoother transition can result in a more natural blend.

exposure_offset_low

A float parameter that adjusts the exposure offset for the low exposure image. It ranges from -6.0 to 0.0, with a default value of -2.0. This adjustment helps in fine-tuning the brightness of the low exposure image.

exposure_offset_high

A float parameter that adjusts the exposure offset for the high exposure image. It ranges from 0.0 to 6.0, with a default value of 2.0. This adjustment helps in fine-tuning the brightness of the high exposure image.

exposure_offset_mid

A float parameter for adjusting the exposure offset of the optional middle exposure image. It ranges from -6.0 to 6.0, with a default value of 0.0. This ensures all exposures are normalized to the same scale before blending.

ghost_removal

A boolean parameter that, when enabled, attempts to remove ghosting artifacts that can occur when blending images with moving elements. The default value is False.

◎ Radiance HDR Exposure Blend Output Parameters:

blended_hdr

This output is an image tensor representing the final blended HDR image. It combines the best details from the input exposures, offering a balanced and detailed representation of the scene.

blend_mask

This output is an image tensor that acts as a mask, showing the contribution of each exposure in the final blend. It can be useful for understanding how different areas of the image were combined.

blend_info

This output is a string providing information about the blending process, such as the method used and dynamic range statistics. It offers insights into the blending operation and can be useful for debugging or analysis.

◎ Radiance HDR Exposure Blend Usage Tips:

• Experiment with different blend methods to find the one that best suits your image. Mertens Fusion is often a good starting point for natural-looking results.
• Adjust the shadow and highlight weights to emphasize specific areas of your image. Increasing shadow weight can bring out more detail in dark areas, while increasing highlight weight can enhance bright areas.
• Use the transition smoothness parameter to control the blending between exposures. A smoother transition can help avoid harsh lines or unnatural blending.

◎ Radiance HDR Exposure Blend Common Errors and Solutions:

"Input tensor dimensions do not match"

• Explanation: This error occurs when the input tensors for low, high, or mid exposures have different dimensions.
• Solution: Ensure that all input tensors have the same dimensions before passing them to the node.

"Invalid blend method specified"

• Explanation: This error occurs when an unsupported blend method is provided.
• Solution: Check the blend method parameter and ensure it matches one of the supported methods: "Mertens Fusion," "Luminance Weighted," "Shadow/Highlight Mask," or "Exposure Weighted."

"Negative HDR values detected"

• Explanation: This error indicates that the resulting HDR image contains negative values, which are not valid.
• Solution: Ensure that the input exposures are correctly adjusted and that the blending process does not introduce negative values. Adjust exposure offsets if necessary.