We present theoretical surface-brightness fluctuations ( SBF ) amplitudes for single–burst stellar populations of young and intermediate age ( 25 Myr \leq t \leq 5 Gyr ) , and metallicities Z = 0.0003 , 0.001 , 0.004 , 0.008 , 0.01 , 0.02 , and 0.04 .
The fluctuation magnitudes and colors as expected in the Johnson–Cousins ( UBVRIJHK ) photometric system are provided .
We pay attention to the contribution of thermal–pulses asymptotic giant branch ( TP–AGB ) stars .
The sensitivity of the predicted SBF to changes in the mass–loss scenario along the TP–AGB phase is examined .
Below 0.6 - 1 Gyr both optical and NIR SBF models exhibit a strong dependence on age and mass loss .
We also evaluate SBF amplitudes by using Monte Carlo techniques to reproduce the random variation in the number of stars experiencing bright and fast evolutionary phases ( Red Giant Branch , AGB , TP–AGB ) .
On this ground , we provide constraints upon the faintest integrated flux of real stellar populations required to derive reliable and meaningful SBF measurements .

We analyze a technique for deriving SBF amplitudes of star clusters from the photometry of individual stars , and estimate the indetermination due to statistical effects , which may impinge on the procedure .
The first optical SBF measurements for 11 Large Magellanic Cloud ( LMC ) star rich clusters - with age ranging from few Myr to several Gyr - are derived by using Hubble Space Telescope observations .
The measurements are successfully compared to our SBF predictions , thus providing a good agreement with models of metallicity Z = 0.0001 –0.01 .
Our results suggest that , for TP–AGB stars , a mass loss as a power-law function of the star luminosity is required in order to properly reproduce the optical SBF data of the LMC clusters .
Finally , near–infrared models have been compared to available data , thus showing the general trend is well fitted .
We suggest how to overcome the general problem of SBF models in reproducing the details of the near–infrared SBF measurements of the Magellanic Cloud star clusters .