Forward modeling tests for DEM reconstruction with XRT channels. In the left column, the fits of single-temperature component DEMs are shown centered at log T = 6.2, 6.7, 7.0 and with the width Δlog T = 0.1. In the right column, the fittings for several multi-temperature DEMs are given. The model DEMs (solid lines) are compared with the reconstructed ones for three groups of XRT channels: the diamonds (left column) and diamonds with dashed line (right column) indicate the solutions for the nine XRT filters with standard calibration; the pluses and pluses with dotted line represent the five XRT filters with standard calibration; the circles and circles with dash-dot line stand for the five XRT filters with calibration of Reale et al. (2009). The DEMs are given as normalized distributions ρ(T) in units of [K^-1].