Spiral galaxies appear to exhibit a large range in properties
 such as disk surface brightness, disk scale length, star
 formation rate and gas surface density. Most of the galaxies
 studied best so far are those with the highest surface brightness.
 It has become quite clear recently that galaxies with low surface
 brightness disks are at least as numerous as the well studied
 high surface brightness galaxies, and understanding their evolution
 is very crucial. We have good photometric data and HI imaging for
 a large number of galaxies over a range of 4 mag/arcsec^2 in surface
 brightness. For the interpretation of the photometry and other
 properties it is important to have a good measure of the FIR
 spectral energy distribution of the galaxies. From our study we
 know that the star formation rate, the gas surface density and
 the metallicity of the Inter Stellar Medium (ISM) decrease with
 decreasing surface brightness of the disk. At the extreme end one
 has the genuinely low surface brightness (LSB) galaxies with very
 low gas surface densities, metallicities of 0.2 - 0.5 solar and
 extremely low star formation rates.
 Little is known about how the dust properties in galaxies vary with
 the surface brightness of the disk. The lower surface brightness
 objects have not been detected in IRAS, probably because the dust
 is much cooler than in high surface brightness (HSB) galaxies and
 the gas-to-dust ratio may be down by a factor 10.

 We propose to observe a sample of 21 galaxies with central surface
 brightnesses of 20 - 24 B-mag/arcsec^2 at 60, 100, 135 and 200
 micron in order to determine the properties of the dust as a
 function of surface brightness and star formation rate.