Reinhard colour mapping workflow?

[jow]

Hey Natty, How's things? U keeping busy..
Dropping the burn value that low, wouldnt it be the same effect as using Exponential mapping?
Do you compensate for this with higher light multiplers?

[vlado]

I think reinhard may be employing gamma 2.2 by default so it would be LWF without the SRGB button. However, Jow me be recompensating for that value by adjusting the multipliers and checking the sRGB button.

It's a question left for Vlado/Peter.

The Reinhard color mapping does not apply any gamma transformation on the result. Here are some curve graphs demonstrating how different color mapping modes work. The x axis is the input (original) image color, and the y axis is the output (color-mapped) color.



Useful observations:

• In the last image, although this is not clear from the limited graph window, neither the Exponential, nor the Reinhard with Burn 0.0 curve ever go above the 1.0 (white) value (e.g. no burnt-out areas). However, the Exponential graph goes very close to white very quickly, while the Reinhard curve is more gradual.
  
• Near the dark colors, the slope for both Exponential and Reinhard modes is similar to the slope of the linear mapping, which means that those modes preserve darker colors near their original value.
  
• When the Burn value is 0.5, the Reinhard curve intersects the y=1 line (the white color) when x=2 (the original color has an intensity of 2); when the Burn value is 0.2, the curve intersects the white line for x=5; the same relationship is true for any other color and allows you to choose presicely the values of the colors that you want to be mapped to white.

Here are larger versions of the images:

http://www.spot3d.com/vray/images/re...ard_burn10.png
http://www.spot3d.com/vray/images/re...ard_burn05.png
http://www.spot3d.com/vray/images/re...ard_burn02.png
http://www.spot3d.com/vray/images/re...ard_burn00.png
http://www.spot3d.com/vray/images/re...xponential.png

Best regards,
Vlado

[panthon]

[Neilg]

That was suprisingly informative in general, thanks.

[jow]

Thanks for explaining what the burn value does Vlado, what about the multipler? Is this similar to what the light/dark multiplers do for the other colour mapping types?

[vlado]

Thanks for explaining what the burn value does Vlado, what about the multipler? Is this similar to what the light/dark multiplers do for the other colour mapping types?

It is just a multiplier to scale the values up and down globally.

Best regards,
Vlado

[jow]

Thanks Vlado.

[muzzy]

that really helped Thanks Vlado

[jujubee]

So then Reinhard at default values is the same as Linear Multiply? At least it appears that way when I have the preferences set up for Linear Workflow.

[DaForce]

Awesome info Vlado!!!

[vlado]

So then Reinhard at default values is the same as Linear Multiply?

Yep, if the Burn is at 1.0, and the multiplier is also 1.0, you get the same result as with Linear mapping.

Best regards,
Vlado

[RePlay]

Thanks Vlado. That was helpful

[tricky]

So, to try and conclude:

For 'well balanced' images, Reinhard with the default values should give a linear mapping look.
To control the way the brightnesses are mapped and prevent colours becoming too blown out too quickly, we use the burn value, where a burn value of 1.0 gives a linear result and a burn value of 0.0 scales the brighter values down so they are not 'out of range' or clipped.
Therefore, values between 0.2 and 0.8 (for example) should allow a good compromise between the blown out look of linear and the washed out look of exponential.

-------------------------------------------- (line drawn under that!)

Before 1.5, we always had the Max gamma set to 2.2 and then we used the Gamma colour mapping with 0.4545 as a value. For all 'colour swatch based materials' (ie, no bitmaps) we used the ColorCorrect plugin to ensure the colour of the swatches was mapped to a gamma of 2.2. This gave us pretty reliable images and gave a good amount of detail in the shadows.

Now with 1.5, will the above Reinhard settings achieve a similar level of detail in the shadows, and if so, should the Max Gamma settings remain at 2.2 with the ColorCorrect plugin for all colour-swatch based materials?

[vlado]

Gamma correction by itself does not deal with the bright areas (e.g. what was overbright before gamma correction, will be overbright with gamma correction as well). That's where Reinhard color mapping comes into play. It will preserve the dark areas like I mentioned in my post, so if you use it together with the gamma 2.2 mapping, I guess it should be fine.

Best regards,
Vlado

[tricky]

okay, but to clear it up for me, what is a description of Gamma Correction color mapping?