Published online by Cambridge University Press: 14 August 2015
The combination of deep photography using fine-grain emulsions and fast automated plate-measuring machines is proving to be a valuable tool in studying galaxy evolution. Until recently, the favoured method for monitoring evolution was the spectroscopic study of one type of galaxy at various redshifts (see Spinrad 1977 for a review). It is considerably more economical, however, to derive evolutionary information from the statistical properties of the numerous faint images detectable on deep plates. The drawbacks are that the data at each apparent magnitude involves galaxies of different types seen over large redshift ranges. Also to interpret the statistics, we need to know the properties of large numbers of galaxies, for example their luminosity function, ultraviolet spectra and, particularly, the morphological variations in such properties.