I suppose it reduces the difference between the 2 types of light source.

A slightly different question.

I was looking at one of my pyro negatives recently and thought it had been scratched. But it was just the so-called "etching" effect on the surface of the emulsion where there are large density changes, in this case branches against cloudy sky. It is a result of the tanning.

I have often wondered if this surface relief has an optical effect with condenser enlargers. My experience when i went from condenser to cold light was that scratches were less apparent, so the relief might do something like accentuate edge effects with condenser light source. I no longer have a condenser enlarger, but has anyone made such a comparison?