These allow to study the distribution of the stellar mass distribution in an optimal manner. It was demonstrated that a variable mass-concentration exponent is necessary to give a good description of the bulge profiles. A fit with a fixed exponent does not give an adequate result. The main results were that bright disks have larger scale lengths, bulges show the same dependency. Bulges and disks populate the same strip in the fundamental plane.
Bright bulges are also less concentrated, the exponent is smaller.
The structural parameters of the bulges form a photometric plane in the space. The existence of this narrow plane is a further hint to a common formation scenario of all types of spiral galaxies. We are grateful to the Calar Alto team for the effective support during the observations.