  Thermal photons from the QGP provide important information about the
interaction among plasma constituents. The photon production rate from a
thermally equilibrated system is proportional to the transverse spectral
function $\rho_T(\omega=|\vec k|, \vec k)$. One can also calculate the photon
production rate from the difference between $\rho_T(\omega,\vec k)$
(transverse) and $\rho_L(\omega,\vec k)$ (longitudinal) projections, as
$\rho_L$ vanishes on the photon point. Because the UV part of $\rho_T-\rho_L$
is suppressed, the corresponding Euclidean correlator receives most of its
contribution from the IR part. We calculate the $T\!-\!L$ correlator on
$N_f=2+1$ flavour HISQ configurations with $m_l=m_s/5$ at temperature of about
$1.15\,T_{pc}$ (220 MeV). We have used two ans\"{a}tze for the spectral
function: 1) A polynomial connected to the UV region consistent with OPE
expansion and 2) a hydro-inspired spectral function. We have also applied the
Backus-Gilbert method to estimate the spectral function. All these different
approaches are combined to estimate the photon production rate.
