CoronaLightMaterial - Take into account camera white balance?

[alexyork]

Here's one for you that might well have been asked before (quick search doesn't turn anything up):

I have a scene setup through, as always, CoronaCameraMod with the WB set appropriately. I then include a CoronaLightMaterial with a texture map on it - it's just a simple plane and the texmap is a simple black and white image. I set the multi to 2 and it looks bright as expected, but it looks really cold compared to the scene around it. Seems that it is not being taken into account by the WB value of the camera, so it remains completely monochromatic in the render where I would expect it to be warm like the rest of the scene.

I am guessing that any CLightMat behaves like this when you use a texture map, is this correct?

Can anything be done to "fix" this? The only work-around I can think of right now is to manually colour-correct the texmap so it looks warm, but this still won't solve the problem if you need to re-shoot the scene in a different WB.

Cheers,

[pokoy]

Do you mean setting the kelvin temp for a bitmap? I think this should be possible with a composite map (probably best in color mode...?) but I agree that having the kelvin temp to work on bitmaps wouldn't be bad.

[alexyork]

Do you mean setting the kelvin temp for a bitmap? I think this should be possible with a composite map (probably best in color mode...?) but I agree that having the kelvin temp to work on bitmaps wouldn't be bad.

Will give that a try but yeh I think it should always just naturally take into account the WB of the camera, just like every other kind of material does. It currently seems very unphysical.

[Juraj]

Sounds quite strange, I think it works correctly. I always use it with CoronaColor set to Temperature in the slot and it behaves accordingly to camera white balance. For example if I set the CoronaColor to 2800K, and then the Camera WhiteBalance likewise, it becomes white.

If you use B/W map, it's basically as using 6500K, which is very cold light. You would have to set your Camera White Balance into very high temperature (like 9000K) for it to appear warm. Maybe your current difference is just too small to make it noticeable ?

Or do you mean the actual directly visible light source (and not the light thrown) ? I believe that one is almost always desaturated because of the Reinhard tonemapping. By the time the light-source it powerful enough to become visible, it's just burned into desaturated whiteness, which appears cold. I use RaySwitch material to overcome this, but filmic mapping makes it appear less drastically desaturated.

[alexyork]

Or do you mean the actual directly visible light source (and not the light thrown) ? I believe that one is almost always desaturated because of the Reinhard tonemapping. By the time the light-source it powerful enough to become visible, it's just burned into desaturated whiteness, which appears cold. I use RaySwitch material to overcome this, but filmic mapping makes it appear less drastically desaturated.

I think this is it - it's the direct visible texture map driven by CLightMaterial. It's not emitting any light.

[Juraj]

You might need some glow/glare for bright light source to appear warm. Otherwise it will look white (and cold) in every correctly exposed version, that is correct behaviour. It will show color directly on its surface only if it's dim.

[denisgo22]

Is possible to make Intensity of LC accordingly to Physical Camera exposure /same in Vray-Compensate Camera Exposure///

[alexyork]

You might need some glow/glare for bright light source to appear warm. Otherwise it will look white (and cold) in every correctly exposed version, that is correct behaviour. It will show color directly on its surface only if it's dim.

It's really not even that bright at all. It's a back-lit LED panel and the brightness is just about right. I will try to post an example later so you guys can see what I mean.

[maru]

Look like everything is ok.

[alexyork]

Thanks Maru, that does look correct to me too. Is that a tex map in there? And you're just changing the multi?

[pokoy]

I guess it's that in case of overbright pixels the displayed color will be white. If you have a bright blueish light and its RGB values are 2/2/5 then it'll come out as white since it's clamped at 1/1/1. That's perfectly visible iin Maru's example.

[maru]

Thanks Maru, that does look correct to me too. Is that a tex map in there? And you're just changing the multi?

Yup, I tried doing it as you described - Corona Light with a texmap loaded - greyscale bitmap. CameraMod, changed color temp.

[Juraj]

There is trick Ondra gave me 2 years ago which retains saturation at any exposure like halogen-type light. It's using HDR values in CoronaColor (as suggested above, in composite if you want to use texture) nested inside LightMaterial.