Do wall surfaces that have already been painted need to be primed again when they receive a new coat?

If wall and ceiling surfaces are to overhauled an to receive a new coat after several years, the question arises as to whether priming is necessary. We recommend the following procedure:

If the new coat is to be applied in approximately the same shade as the existing coating, you do not need a primer.

However, if the new color tone differs greatly from the existing paint, we recommend priming:

In this case, the primers provide the necessary opacity and the corresponding color brilliance of the topcoat.