In a method to determine a negative effect on a surface of an image carrier of a print group, a reflection spectrum is determined of a region of the surface of the image carrier, the reflection spectrum indicating an intensity of light for different wavelengths. The light is reflected from the region of the surface of the image carrier. A reference spectrum is determined for the region of the surface of the image carrier. The reflection spectrum is then compared with the reference spectrum. Depending on the comparison, the determination is made whether a negative effect is present at the region of the surface of the image carrier.