  A 0.35\degr $\times$ 0.29\degr field centered at $l$=--18.63\degr,
$b$=0.35\degr was observed during the ISOGAL survey by ISOCAM imaging at
7$\mu$m and 15{\rm $\mu$m}. 648 objects were detected and their brightness are
measured. By combining with the DENIS data in the near-infrared J and K$_{\rm
S}$ bands, one derives the extinction at 7{\rm $\mu$m} through ${\rm A_{K_{\rm
S}}-A_7= 0.35 (A_J-A_{K_{\rm S}})}$ which yields A$_{7}$/A$_{\it V}$ $\sim$0.03
from the near-IR extinction values of van de Hulst--Glass (Glass 1999). The
extinction structure along the line of sight is then determined from the values
of J--K$_{\rm S}$ or K$_{\rm S}$--[7] of the ISOGAL sources identified as RGB
or early AGB stars with mild mass-loss. The distribution of A$_{\it V}$ ranges
from 0 to $\sim$45 and it reflects the concentration of the extinction in the
spiral arms. Based on their locations in color-magnitude diagrams and a few
cross-identifications with IRAS and MSX sources, the nature of objects is
discussed in comparison with the case of a low extinction field in Baade's
Window. Most of the objects are either AGB stars with moderate mass loss rate
or luminous RGB stars. Some of them may be AGB stars with high mass loss rate.
In addition, a few young stellar objects (YSOs) are present.
