Thanks for jumping in too, Stephen! What I actually meant about the light source being defined as super crisp in the ies file is that there’s a seeming sharpness in the candela values that is creating the same or similar hard edges as you see when using the Radiance light primitive. But your catch about the zero reflectance should make a huge difference in smoothings out and softening some of these shadows.
As I’d mentioned previously, the -ds won’t make a huge difference in this case, that is more critical for linear and large area sources.
Lastly, your question about the color temperature. This is why it is recommended that you use WHITE for all your light source specs in ies2rad. Color fidelity in this case is extremely difficult to depict on the display device, and when you have multiple sources of different CCTs in the same Radiance image it gets even hairier, and pcond -h can only do so much. It’s the topic of a masters thesis at least, and Greg is way better at explaining the details and the whys of it all. In short, Radiance is showing you the result of doing all the spectral accounting from pixel to source, but our eyes do a color balance in Real Life that’s not being done here.