Color Mapping

• General
• Parameters
• Notes

 

Search keywords: color mapping, tone mapping, burn-out, overexpose

General

It seems that real world photography and the human eye sees a bit different than a pure digital produce image. It can adjust to different light levels and contrasts, so the eye can compensate rather good dark indoor rooms p.e. after a short while they eyes “color mapping” is adjusted and you see also the darker parts of the environment. also different film paper types have not a linear behavior to colors and light, the perception of the eye might also not be linear, and also our screens of today have a non linear gamma of 1.8 to 2.2. So we have probably many things to consider there are many different approaches and theories, one of them the “linear workflow” LWF. No all professional believe the LWF is correct, but it definitely tries to solve some problems seen with digital produced imagery.

Others use their own methods of color mapping and gamma adjustments. However, in most of this methods some kind of gamma adjustment or gamma recorrection for textures and the screen are used. camera mapping can help a lot for this or for simulating different film behavior.

For architects specially in indoor scenes can get improved much by the right use of color mapping.

For cinematographic use you may want to compensate the GI light to have a bit more contrast so you can push the dark tomes etc...

In VRAYforC4D the special thing is that the color mapping is not a simple post process, but really changes the way the light is computed in the GI solution. make some tests at start of  the scenes to find the correct settings for your need. also note that different color mapping settings might lead to longer render times. often color mapping is used in combination of adjusting the input of material colors. p.e. some people like to get rid of the 2.2 gamma many images have already implied due to the 2.2 screen gamma. to compensate this you can use the c4d filter shader and reduce gamma to 0.4545 (1/2.2).

We cannot give any instant solution here fro all kinds of use, but color mapping is definitely an interesting aspect in trying to achieve most realistic imagery. The color mapping should be used with care and might so not be an dramatic effect, but often the slight differences make the big difference at the end.

Parameters

Type - this is the type of transformation used. These are the possible types: 

Linear multiply - this mode will simply multiply the final image colors based on their brightness are. Color components that are too bright (above 1.0 or 255) will be clipped. This can result in burnt out spots near bright light sources.

 

Exponential - this mode will saturate the colors based on their brightness. This can be useful to prevent burn-outs in very bright areas (for example around light sources etc). This mode will not clip bright colors, but will instead saturate them.

 

HSV exponential - this mode is very similar to the Exponential mode, but it will preserve the color hue and saturation, instead of washing out the color towards white.

 

Intensity exponential - this mode is similar to the Exponential one, but it will preserve the ratio of the RGB color components and will only affect the intensity of the colors.

 

Gamma correction - this mode applies a gamma curve to the colors. In this case, the Dark multiplier is a general multiplier for the colors before they are gamma-corrected. The Bright multiplier is the inverse of the gamma value (f.e. for gamma 2.2, the Bright multiplier must be 0.4545).

 

Intensity gamma - this mode applies a gamma curve to the intensity of the colors, instead of each channel (r/g/b) independently.

 

Reinhard - this mode is a blend between exponential-style color mapping and linear mapping. If the Burn value is 1.0, the result is linear color mapping and if the Burn value is 0.0, the result is exponential-style mapping.

 

Dark multiplier - this is the multiplier for dark colors.

 

Bright multiplier - this is the multiplier for bright colors.

 

Gamma - this parameter allows the user to control the gamma correction for the output image regardless of the color mapping mode. Note that the value here is the inverse of the one used for the Gamma correction color mapping type. For example, to correct the image for a 2.2-gamma display, you should set the Gamma parameter simply to 2.2.

 

Sub-pixel mapping - this option controls whether color mapping will be applied to the final image pixels, or to the individual sub-pixel samples. In older versions of VRAYforC4D, this option was always assumed to be on, however its default value is now off as this produces more correct renderings, especially if you use the universal settings approach.

 

Clamp output - if this is on, colors will be clamped after color mapping. In some situations, this may be undesirable (for example, if you wish to antialiasing HDR parts of the image, too) - in that case, turn clamping off.

 

Clamp level - this option specifies the level at which color components will be clamped if the Clamp output option is on.

Adaptation only - when this parameter is on, the color mapping will not be applied to the final image, however VRAYforC4D will proceed with all its calculations as though color mapping is applied (e.g. the noise levels will be corrected accordingly). This can be useful, for example, if you know that you will apply some color correction to the image later on, but wish to keep the rendering itself in linear space for compositing purposes. Note that the Clamp output option will have an effect regardless of the value of the Don't affect colors option.

 

Affect background - if this is off, color mapping will not affect colors belonging to the background.

Notes

• For Linear workflow you must set Gamma parameter to 2.2. and filter every material in scene with C4D Filter applying with gamma 0.454 (for PC).