In SpectraProof, you can not only measure the paper whites of substrates and have them simulated as modified paper whites in the softproof, but you can also easily use entire papers with their specific surfaces, such as kraft or cotton, linen papers with distinct surface textures, or recycled papers with their open surface, for a photo-realistic simulation.
You can easily scan new substrates and import them into SpectraProof as image files. Over time, you can build up a paper and substrate archive of the materials you use, which you can then use for colour-accurate simulation in SpectraProof.