Complex sentence: The Tate and the National Gallery investigated the use of PTMs and determined that they could be viable alternatives to raking light; especially since PTMs were found to be more easily replicated than raking light photographs.
Split into simpler sentences: The Tate and the National Gallery investigated the use of PTMs and determined that they could be viable alternatives to raking light. Especially since PTMs were found to be more easily replicated than raking light photographs.