  This paper discusses some of the challenges of spectro-polarimetric
observations with a large aperture solar telescope such as the ATST or the EST.
The observer needs to reach a compromise among spatial and spectral resolution,
time cadence, and signal-to-noise ratio, as only three of those four parameters
can be pushed to the limit. Tunable filters and grating spectrographs provide a
natural compromise as the former are more suitable for high-spatial resolution
observations while the latter are a better choice when one needs to work with
many wavelengths at full spectral resolution. Given the requirements for the
new science targeted by these facilities, it is important that 1)tunable
filters have some multi-wavelength capability; and 2)grating spectrographs have
some 2D field of view.
