Brightness of bitmap/light material differs

[Bondra]

Can someone explain why the brightness between the original bitmap and the one in the scene differs? Settings are default and the material I'm using for the backplate is a light material. I sure can tweak the settings to get them more alike but is this really needed? Shouldn't the light material in this case pretty much show the original image as is?

This is what it looks like:

[romullus]

If you want you background image to be unaffected by scene exposure and/or tone mapping, plug it to Corona tonemap control texmap and uncheck according options.

[maru]

Romullus suggested using the Corona Tonemap Control node and that's because all textures/materials (including the LightMtl) are by default affected by Corona's post processing and tone mapping settings.
See: https://docs.chaos.com/display/CRMAX/Corona+Tonemap+Control+Map

[Bondra]

Thank you! Just what I was looking for! Followed the material setup and it works but think I maybe stumbled across a bug with the IR? Increasing the value for, say Simple Exposure in the Corona VFB makes it all bright (the bitmap included) til I slightly move the camera in the viewport and the IR updates again. Then the bitmap goes back correctly and unaffected.

[romullus]

That's how it works. You could easily find this yourself if you'd spend couple minutes to read documentation.