0.123 = - log T
T =
if you mean log to the base 10, then 0.123 = -logT means that T = 10-0.123 or
$${\mathtt{T}} = {{\mathtt{10}}}^{-{\mathtt{0.123}}} \Rightarrow {\mathtt{T}} = {\mathtt{0.753\: \!355\: \!563\: \!733\: \!717\: \!4}}$$