We give here a more detailed description of the *differential
correction* algorithm discussed in Sect. 4.3.

For each model spectrum and given parameter values in the grid, we proceed along the following steps:

- 1.
- we compute the synthetic colors, , from the
original theoretical energy distribution, , and the normalized response functions of the filters,
, (Eq. 6) by
(13) - 2.
- as described in detail in LCB97, these theoretical colors, and hence
the monochromatic fluxes within each wavelength band, are then used to
calculate the
*theoretical*pseudo-continuum, , as a black-body with smoothed color temperatures, , varying with wavelength:(14) - 3.
- from the theoretical colors, , we compute
the
*theoretical color differences*,(15) (16) - 4.
- by adding these color differences to the empirical colors,
given in Table
1, we then define the
*semi-empirical*colors, :(17) - 5.
- from Eq. (14), these
*semi-empirical*colors allow us to calculate the*semi-empirical*pseudo-continuum, ; - 6.
- a ``spectral function'', , which
contains the high-resolution information of the theoretical spectrum,
is defined by the ratio of the original spectrum and the theoretical
pseudo-continuum,
(18) - 7.
- the
*corrected*spectrum is finally computed by multiplying the spectral function with the semi-empirical pseudo-continuum:(19)

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