Incarnadine: TA stands up pretty well but IMO needs to be dimmed a bit... ...I don't remember if you can adjust TA in this manner. Anyone know? My image is as much a representation of my errors as it of what True Ambience can do. Much of the interior is too bright in relation to the light potential from the windows because I made a poor choice of light levels; and not due to any inherent fault of TA. As I stated above, I made a best assessment on the basis of first render passes and stuck with what looked best under those limiting circumstances. Restarting wasn't an option once the image began to become clear, due to the render time commitment involved. In this case, the illumination could be better balanced simply by reducing the intensity of the lights along the long ceiling. There would be no need to alter True Ambient levels at all. Reducing the ambient levels of materials is how you 'trim back' the effect of True Ambience. In the first image, levels are 100 percent. In my second image, levels are effectively at zero because I disabled True Ambience. This shows the range available. Based on shooting in several cathedrals, the interior is dim generally with awesome light from the windows. Yes, as I alluded to above, all these images would benefit from more light saturation at the windows to be 'photo-realistic'. With photography you could make the interior as light as you wanted by using longer exposure times. But the longer the exposure, the more light saturation at the windows there would be.