Tone Mapping Operators

When rendering with Corona, you can use different Tone Mapping operators to process and improve the overall look of your image. Each operator can be enabled or disabled according to your needs.

Instructions on how to manipulate operators are as follows:

• To add a new operator, use the + button.
• To remove any operator, right-click on it and then use the Delete option.
• To set all operators and their values to the default ones, use the Reset button.
• Additionally, as a starting point, use the Presets button to load any of the already provided combinations of operators, then decide if they work for you or if they need to be fine-tweaked.

Simple Exposure – Changes the overall exposure of the image. Value range: from -20 to 20.

White Balance – Sets the white balance point using Kelvin temperature, often used in photography. Lower temperature leads to a bluish, cold appearance of the image, while higher temperature leads to a warm appearance. Value range: from 2000 to 99999.

Green-Magenta Tint – Applies green-magenta tint - the complement of temperature in white balance. Setting a negative value will result in a magenta-looking picture, while a positive value will lead to a greenish picture. The default value of 0.0 has no effect. Value range: from -1 to 1.

Contrast – The difference in brightness between light and dark areas of the image. Values greater than 1 increase the image contrast, and values below 1 decrease it. Value range: from 0 to 99.

Saturation – Controls the overall image saturation. Positive values increase image saturation; negative values decrease it. Value range: from -1 to 1.

ACES OT – Applies approximate ACES Output Transform, which consists of Reference Rendering Transform (RRT) and Output Device Transform (ODT). Value range: from 0 to 1.

Photographic Exposure – Changes the overall exposure of the image based on the settings of the currently used camera.

Tint – Sets the overall color tint of the scene. The entire image is multiplied by this color. This can be used both to add and remove color tint from the image. To add a tint, just select the color of the tint directly. To remove tint from any rendered object, pick its color using the "pick inverse" eyedropper in Corona Improved Color Picker.

Vignette - Simulates real-world camera vignette by darkening the edges of the image. Value range: from 0 to 10

Advanced Filmic Mapping – Applies highlight compression and shadow saturation control using Filmic S-curve. Allows more control over the curve compared to the basic Filmic operator. When enabled, the output is always in the interval [0,1], so the bright pixels are compressed.

• Toe Strength – The values in the toe (the leftmost segment of the S-curve) are squeezed into a smaller output range. The stronger the toe, the smaller the interval. 0 means there is no toe, and 1 means that the toe is completely flat on the x-axis, assigning 0 to all values in the toe.
• Toe Lenght – The values in the toe (the leftmost segment of the S-curve) are squeezed into a smaller output range. The longer the toe, the more values are affected, starting from the darkest values. 0 means no toe, and 1 means that the toe takes up half the curve.
• Shoulder Strength – Stretches the dynamic range of the curve - moves the white point to higher input values. The values above the white point are simply clamped to white. 0 means no shoulder - the white point is where the linear middle part reaches 1. The parameter describes how many F stops we add to the dynamic range.
• Shoulder Lenght – The values in the shoulder (the rightmost segment of the S-curve) are squeezed into a smaller output range. The longer the shoulder, the lower values are assigned, starting from the brightest values. 0 means there is no shoulder starts where the toe ends (there is no linear part in the middle).
• Shoulder Angle – Increasing the steepness of the shoulder. The reason is that a long flat shoulder squeezes too wide dynamic range into a narrow range in output values causing the loss of contrast in the bright parts of the image. Increasing this parameter leads to the white point being higher than 1; therefore, the curve is then rescaled so the output values are in [0,1].
  
  

Curves – Applies custom color mapping curves.

Filmic Mapping – Allows highlight compression and shadow saturation control using Filmic S-curve.

• Highlight compression – Applies a filmic tone mapping to bright regions of the image, resulting in subtle highlight compression without loss of color saturation.
• Rich Shadows – Applies a filmic tone mapping to dark regions of the image, resulting in increased richness/saturation of shadows.

Tone Curve – Allows independent control of different tones of the image - shadows (the darkest areas), darks, lights, and highlights (the brightest area).

• Highlights – Adjust the brightest areas of the image. Positive values enhance them, while negative values suppress them. This affects the brightest subset of the tones that the "lights" parameter affects.
• Lights – Adjust the bright areas of the image. Positive values enhance them, while negative values suppress them. This affects a wider range of tones than the "highlights" parameter.
• Darks – Adjust the dark areas of the image. Positive values enhance them, while negative values suppress them. This affects a wider range of tones than the "shadows" parameter.
• Shadows – Adjust the dark areas of the image. Positive values enhance them, while negative values suppress them. This affects the darkest subset of the tones that the "darks" parameter affects.

Reinhard Highlight Compression – Compresses highlights in the image to reduce/remove burned-out areas. Increasing the value removes burned-out areas, and decreasing it amplifies highlights.

ACES Output Transform – Applies approximate ACES Output Transform, which consists of Reference Rendering Transform (RRT) and Output Device Transform (ODT).

LUT – Changes the overall look of the image by applying a predefined LUT.

• Opacity – Sets the opacity of the LUT transform. Value 0.0 does not change the result at all, while the default value 1.0 applies the full-color transform according to the selected LUT file.
• Logarithmic – If enabled - the image is converted to the logarithmic color space, and only after that, the LUT is applied.