@barucden just out of curiosity, did you need to restrict to 1.5 for latex purposes? If so,
\pdfminorversion=7 % needs to be before the documentclass (i.e. pdf can not be started)
in the preamble (or pre-preamble?) should allow you to use later pdf versions.
For example
\pdfminorversion=7
\documentclass[aspectratio=1610]{beamer}