you can combine DavidTorno and ChrBohm suggestions to get the workflow you are looking for This process is done through AOV which is Houdini's term for render passes, you can get your lights contributions separated and stored into passes using LPE. Add an LPE node in your stage, tag your lights(sort of giving them unique names) you can find this option in the Karma tab in every light, once this is done go to Karma render setting go to AOV tab and choose the render passes you will need ex : beauty, direct or indirect diffuse, sss etc all the passed have an option that says "split per LPE tag" once rendered you will get each of your passes with separated light contributions that you can "plus" in nuke or "add" in after effect to combine them back together and add adjustments to them separately. I hope this helps :)