  Recent applications have proved that the Surface Brightness Fluctuations
(SBF) technique is a reliable distance indicator in a wide range of distances,
and a promising tool to analyze the physical and chemical properties of
unresolved stellar systems, in terms of their metallicity and age. We present
the preliminary results of a project aimed at studying the evolutionary
properties and distance of the stellar populations in external galaxies based
on the SBF method.
  On the observational side, we have succeeded in detecting I-band SBF
gradients in six bright ellipticals imaged with the ACS, for these same objects
we are now presenting also B-band SBF data. These B-band data are the first
fluctuations magnitude measurements for galaxies beyond 10 Mpc.
  To analyze the properties of stellar populations from the data, accurate SBF
models are essential. As a part of this project, we have evaluated SBF
magnitudes from Simple Stellar Population (SSP) models specifically optimized
for the purpose. A wide range of chemical compositions and ages, as well as
different choices of the photometric system have been investigated. All models
are available at the Teramo-Stellar Populations Tools web site:
www.oa-teramo.inaf.it/SPoT.
