Colorized burnouts

[Robert_XSI]

Hi!

Hopefully i can explain my point well. In a real photo, or in a real camera if i overexpose something, which is colored (much saturated red or yellow), then it will turn to complete white.

If i overexpose something in arnold or mental ray, it just stays red or yellow and will never turn to complete white.
It looks so unnatural compared to the real photo.

Can I get the same behavior somehow in arnold or in mental ray?

THX
robert

[Fer]

Well it depend on what color profile you're working on, your depth of field and exposure, I don't know about Arnold, mr have have
a good tone mapping shader (photographic exposure) do you use it ?

But really if you want a more advanced way you should render to full float exr and with some good Zdepth map, and post process to After effects Nuke or Fusion, I'm sure you'll have more option to achieve want you want.

[Robert_XSI]

Thanks Fer for your reply,

Unfortunately if I render it out in exr, and try to increase the explosure in nuke (grade node - multiply parameter), then the color does not go to white, only burns into a complete saturated red or white, and does not behave like in real life. Of course I can fake it by fading it into white, but I wanted a somewhat realistic approach.

THX
robert

[Mathaeus]

as far as I know, it's just the one of conventions, how to display RGB values far over 1. Probably difference is taken somehow, in favor of stronger RGB component, suppressing weak one. If I'm correct, over some (arbitrary) value, you can get only white, or full saturated color. Full saturated = two of RGB components at opposite side of third, no one in between 0 and 1.
In Mental Ray, by activating "desaturate colors when clipping" option(if this is still present), another convention is activated. But I'll try what Fer suggested, lens shader seems to have a much finer control. Or, something that works like mentioned MR lens shader, in comp.

About analog photo, well just this is an area, full of conventions and recipes. Let's say, well known 'Kodak color' was a synonym for slightly over-saturated color, more pleasant than realistic. And digital cameras are trying to simulate the conventions of analog cameras. All in all, I think you shouldn't hesitate to build your own color-mapping recipe.

[gustavoeb]

I think what you are talking about has a lot to do with the color you select. When you increase exposure you are efectivly multiplying the values of your RGB contributions. So for example if you have (1.0, 0.2, 0.1) you will have a very redish color when you in increase the exposure all values are multiplied by some scalar, as red is already maxed out green and blue will catch up, until you eventually hit white. That is what you want.
But if you have 0 contribution in any of the channels you will have nothing to multiply by and will never hit white. Therefore, never have fully saturated values in your emission. I wouldnt have fully saturated values anywhere, as those dont seem to happen often in the real world.
Below are some picters of what I am talking about.

[origin]

what Mathaeus said...and cameras have limited fstops, with cgi you are not limited in any way, so no clipping, no color compression etc
In nuke just plug cc node with highlight range moved outside 0-1 and play with highlight saturation...or key out overexposed values, use it as a mask and desaturate colors