Black edge around light

[ledisnomad]

Hi, I have an interior scene that I was lighting with long lights. I tried linear lights, but they were too noisy. So now I'm working with surface on which I apply an emitting material. It looks nice, but I have two problems: blotchy areas on large smooth surfaces and right around the lights there is a black line. See the image. I have what I consider pretty high quality settings already (IR+LC). Glossy materials on the floor and ceiling, diffuse walls, a standard glass material. Nothing fancy. There is also one point light in the middle of the atrium and a few spot lights around the perimeter.

I think it is the emitting material, but I don't understand why. Any help would be appreciated.

[fpedrogo]

Go to the Color mapping tab and enable the sub-pixel and clamp output options.

Best

[konstantin_chaos]

I think you are using the Catmull-Rom AA filter which is sort of a sharpening operator. There is a big difference between the intensity of the lights and the surrounding materials and the sharpening operation is exaggerating that difference (causing the black edges). Just change the filter to Area or Sinc and you will be fine. If the image is too blurry you can decrease the filter size. Clamping the colors will also decrease the problem but you will loose the high dynamic range of your image.
Hope that helps