Diffuse interstellar bands in low E(B-V) objects

We analyse spectra of slightly reddened, early-type stars in which the major diffuse interstellar bands at 5780 and 5797 Angstrom are either strong or weak in relation to E(B-V). It is demonstrated that among the low E(B-V) objects one can find stars obscured by 'sigma' as well as 'zeta' type clouds. The profiles of the diffuse bands seem not to be dependent on the total opacities of the interstellar clouds. We also discuss the physical conditions leading to the formation of the diffuse band carriers in low-opacity interstellar clouds; the carriers are apparently formed in media in which one can observe complex velocity fields.