Node input.....?

[Shabazzy]

...For such things people invented post-processing

Yes, that's a recommendation that I too suggested.

sound like a job for
Dpont Nodal Image Filter

haven't used it all too much tho'

see >

https://forums.newtek.com/threads/gerardo-estrada-dpont-multipass-rendering-lw11.166143/

i believe you should use a mask node or something, and hook that into the reflection

https://dpont.pagesperso-orange.fr/plugins/nodes/DP_Filter.html#NodeImgFilt

Dpont Nodal Pixel Filter, could also be the solution

sorry, haven't used these much.

You may be right, the problem is the original query came from someone who is very much a vanilla LWer (much like myself) and would rather use its native tools.

You can use 'ray type switch' nodes to do these sorts of tricks in LW 2020, but not sure if these were available in LW2015. I think there were alternative ones though.

No, unfortunately 'ray type switch' is not available in 2015.

Thanks anyway to all who responded to the question, you've pretty much all confirmed my own findings. Either 'fix it in post', use a third party plugin/nodes or use LW2019 / LW2020.