Résumé
Assuming LTE, we investigate the formation of the G band in the semiempirical flux-tube model of Briand & Solanki (1995). Preliminary results agree with observations of G-band bright-point contrast, even though the observed contrast depends sensitively on the amount of scattered light. It is the weakening of spectral lines in the flux tube that makes the bright-point contrast greater in the G band than in ordinary continuum. We also present LTE synthetic spectra for the full wavelength range from UV to IR. This serves to point out other promising pass bands for the observations of flux-tube structures.