###ACS FOIBLES ### * How bad is the fringing at wavelengths longer than 7500 Angstrom ? Like most CCDs, the ACS CCDs show fringing in the red for monochromatic light at wavelengths longer than 7000 Angstrom. The amplitude of the fringes is a strong function of wavelength and source monochromicity. At the time of writing the ACS HAndbook (June 2000), we do not have good figures for the amplitude of the fringing; a preliminary investigation shows that fringing in ACS is less severe than STIS (see ISR Bohlin, Hartig and Tsvetanov, in preparation). Work is in progress to reduce residuals of fringing to <= 1%.