  The nonlinear force-free field (NLFFF) modeling has been extensively used to
infer the three-dimensional (3D) magnetic field in the solar corona. One of the
assumptions in the NLFFF extrapolation is that the plasma beta is low, but this
condition is considered to be incorrect in the photosphere. We examine direct
measurements of the chromospheric magnetic field in two active regions through
spectropolarimetric observations at He I 10830 A, which are compared with the
potential fields and NLFFFs extrapolated from the photosphere. The comparisons
allow quantitative estimation of the uncertainty in the NLFFF extrapolation
from the photosphere. Our analysis shows that observed chromospheric magnetic
field may have larger non-potentiality compared to the photospheric magnetic
field. Moreover, the large non-potentiality in the chromospheric height may not
be reproduced by the NLFFF extrapolation from the photospheric magnetic field.
The magnitude of the underestimation of the non-potentiality at chromospheric
heights may reach 30-40 degree in shear signed angle in some locations. This
deviation may be caused by the non-force-freeness in the photosphere. Our study
suggests the importance of the inclusion of measured chromospheric magnetic
fields in the NLFFF modeling for the improvement of the coronal extrapolation.
