This page provides information on the Tone Mapping operators in Corona for Cinema 4D, their settings, and usage.

Overview

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.

Operators are processed from top to bottom, just like layers in an image editing software. To get different results, you can rearrange the operators by dragging and dropping them into a different place.

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.


Basic Tone Mapping Operators

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.

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

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

Lift Gamma Gain – Applies a Lift, Gamma, and/or Gain correction.

Lift – Makes the darkest parts of the image brighter or darker.

Gamma – Applies gamma correction to the whole image.

Gain – Makes the brightest parts of the image brighter or darker.

Adjusting the Lift and/or Gamma values results in nonlinear output. When composing render elements together, this operator has to be set to the default value of 1.0 to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

Adjusting only the Gain value maintains the linear workflow.

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

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

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

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

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

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. Unlike the ‘Legacy White Balance’ here we compute the white balance using Bradford’s chromatic adaptation formula, which makes it more accurate and in-line with industry standard. Value range: from 2000 to 99999.

Legacy 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.


Starting from Corona 12 Update 1, the White Balance operator has been deprecated and now called "Legacy White Balance." The new White Balance operator uses Bradford's chromatic adaptation formula, which makes it more accurate and in-line with industry standard.

 By default, the following Tone Mapping operators are used for every Corona Camera Tag as a starting point:

  • Simple Exposure
  • White Balance
  • Green-Magenta Tint
  • Contrast
  • Saturation
  • ACES OT


Curve Control Tone Mapping Operators

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 Length – 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 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 Length – 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].

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

This operator lowers the brightness values in the image highlights. If you are planning to save your image in a high-dynamic range format and edit it in post-production, consider disabling this operator.

Curves – Applies custom color mapping curves. 

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

The Curves editor has Pan and Zoom functions. To use the pan function, move the mouse while pressing and holding the middle mouse button, and to use the zoom function, scroll the mouse wheel up/down.


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

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

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

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 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 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.

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

This operator lowers the brightness values in the image highlights. If you are planning to save your image in a high-dynamic range format and edit it in post-production, consider disabling this operator. 


Highlight Control Tone Mapping Operators

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.

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

This operator lowers the brightness values in the image highlights. If you are planning to save your image in a high-dynamic range format and edit it in post-production, consider disabling this operator.


Final look Tone Mapping Operators

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

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.

This operator lowers the brightness values in the image highlights. If you are planning to save your image in a high-dynamic range format and edit it in post-production, consider disabling this operator.


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

  • Opacity – Sets the opacity of the LUT transform. A value of 0.0 does not change the result at all, while the default value of 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.
  • Linear – if disabled (default), the LUT is applied in gamma-mapped color space. If enabled, LUT is applied in linear color space.

The effect of this operator may not be unmapped correctly in the Corona Tonemap Control shader, especially with the logarithmic option enabled or opacity set lower than 1.

Applying this operator results in nonlinear output. When composing render elements together, this operator has to be disabled to get correct results; for example, when using multi-passes that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.



Tone Mapping Operators and Compositing

Please consider that applying any of the following operators results in a nonlinear output.

  • Contrast
  • Saturation
  • ACES OT
  • Advanced Filmic Mapping
  • Curves
  • Filmic Mapping
  • Tone Curve
  • Reinhard Highlight Compression
  • LUT

When composing multi-passes together, these operators need to be disabled to get correct results.

For example, when using render elements that split the output to reflection/refraction, only linear operations should be used before combining those elements back together.







Examples