◎ Radiance Log Curve Encode:
RadianceLogCurveEncode is a node designed to transform scene-linear image data into a log-encoded format, which is commonly used in high dynamic range (HDR) imaging and film production. This transformation is crucial for efficiently compressing the wide range of luminance values found in real-world scenes into a format that can be more easily stored and manipulated. The node leverages specific log curves, such as ARRI LogC3 or LogC4, to ensure that the encoding process is mathematically symmetric, meaning that the encoded data can be accurately decoded back to its original form. This capability is particularly beneficial for maintaining image quality during post-processing workflows, where precise color grading and exposure adjustments are required. By using RadianceLogCurveEncode, you can achieve a more consistent and predictable outcome when working with HDR content, ensuring that the visual integrity of your images is preserved throughout the editing process.
◎ Radiance Log Curve Encode Input Parameters:
source_space
The source_space parameter specifies the color space of the input image data. It determines which log curve will be used for encoding. If the source space is already a log space, the node will use its corresponding curve to ensure a symmetric encode-decode process. If not, it defaults to using the LogC4 curve. This parameter is crucial for ensuring that the encoding process matches the characteristics of the input data, thereby preserving image quality. There are no specific minimum or maximum values, but it typically includes options like "Linear", "LogC3", "LogC4", etc.
exposure_index
The exposure_index parameter is used to adjust the sensitivity of the log encoding process. It is particularly relevant when working with ARRI LogC3, where the exposure index can influence the resulting encoded values. This parameter allows you to fine-tune the encoding to match the exposure settings of the original scene, ensuring that the encoded image retains the intended visual characteristics. The exposure index is typically expressed as an integer value, such as "EI 800".
target_gamut
The target_gamut parameter defines the color gamut to which the encoded image will be transformed. This is important for ensuring that the colors in the encoded image are accurately represented in the desired output color space. Options may include "Native / No Transform", "Linear sRGB (Rec.709)", "Linear P3-D65", and "Linear Rec.2020". Selecting the appropriate target gamut ensures that the encoded image is compatible with the intended display or output medium.
◎ Radiance Log Curve Encode Output Parameters:
encoded_image
The encoded_image parameter represents the log-encoded version of the input image. This output is a float32 tensor that has been transformed using the specified log curve and exposure index. The encoded image is suitable for storage, transmission, or further processing in HDR workflows. It retains the dynamic range and color fidelity of the original scene while being compressed into a more manageable format.
◎ Radiance Log Curve Encode Usage Tips:
- Ensure that the
source_spaceparameter accurately reflects the color space of your input image to achieve the best encoding results. - Adjust the
exposure_indexto match the exposure settings of your original scene, especially when using ARRI LogC3, to maintain visual consistency. - Choose the
target_gamutbased on the intended display or output medium to ensure accurate color representation.
◎ Radiance Log Curve Encode Common Errors and Solutions:
"Log curves are unavailable — falling back to sRGB linearization"
- Explanation: This error occurs when the required log curves are not available, causing the node to default to an incorrect sRGB linearization process.
- Solution: Ensure that the necessary log curve functions are installed and accessible. Check for the presence of
color_utils.pyor similar resources that provide the required log curve implementations.
"Invalid exposure index format"
- Explanation: This error indicates that the exposure index provided does not match the expected format, such as "EI 800".
- Solution: Verify that the exposure index is correctly formatted as an integer prefixed with "EI ". Adjust the input to match this format.
