Thermal photons from the QGP provide important information about the interaction among the plasma constituents. The photon production rate from a thermally equilibrated plasma is proportional to the transverse spectral function $\rho_T(k_0=|\vec k |,\vec k )$. One can calculate the photon production rate also from the difference between $\rho_T$(transverse) and $\rho_L$(longitudinal) correlator as $\rho_L$ vanishes on the photon point. The UV part of $\rho_T-\rho_L$ is suppressed, and therefore the corresponding Euclidean correlator receives most of its contribution from the IR part of $\rho_T-\rho_L$. We calculate the continuum extrapolated T-L correlator using Clover Improved Wilson fermion on the quenched lattices at temperatures 1.1 $T_c$ and 1.5$T_c$. We also calculate the same correlator on $N_f=2+1$ flavor HISQ configurations with $m_l = m_s/5$ at temperature $\sim 1.15T_c$ and $\sim 1.3T_c$. We have used two ansätze of the spectral function, which are 1) Polynomial ansatz of the spectral function connected to the UV perturbative region and 2) Hydro-inspired spectral function. We have also used the Backus-Gilbert method to estimate the spectral function. We will compare the photon production rate estimated from all these different methods.