  Imaging spectrographs are popular instruments used to obtain solar data. They
record quasi-monochromatic images at selected wavelength positions. By scanning
the spectral range of the line, it is possible to obtain bidimensional maps of
the FoV with a moderate spectral resolution. In this work, we evaluate the
quality of spectropolarimetric inversions obtained from various wavelength
samplings during umbral flashes. We computed numerical simulations of nonlinear
wave propagation in a sunspot and constructed synthetic Stokes profiles in the
Ca II 8542 \AA\ line during an umbral flash using the NLTE code NICOLE. The
spectral resolution of the Stokes profiles was downgraded to various cases with
differences in the wavelength coverage. A large set of wavelength samplings was
analyzed and the performance of the inversions was evaluated by comparing the
inferred chromospheric temperature, velocity, and magnetic field with the
actual values at the chromosphere of the numerical simulation. The errors in
the inverted results depend to a large extent on the location of the wavelength
points across the profile of the line. The inferred magnetic field improves
with the increase of the spectral resolution. In the case of velocity and
temperature, low spectral resolution data produce a match of the inverted
atmospheres with the actual values comparable to wavelength samplings with
finer resolution, while providing a higher temporal cadence in the data
acquisition. We validated the NLTE inversions of spectropolarimetric data from
the Ca II 8542 \AA\ during umbral flashes, during which the atmosphere
undergoes sudden dramatic changes due to the propagation of a shock wave. Our
results favor the use of fine spectral resolution for analyses that focus on
the inference of the magnetic field, whereas the estimation of temperature and
velocity fluctuations can be performed with lower spectral resolution.
