If you create a Drop Shadow between 19 - 55 mm in size and export the page as PDF-X3 with 300 dpi, the full resolution is not rendered (check with Acrobat Pro DC - Preflight with image resolution check). Under 19 mm and over 55 mm everything is OK. Tested on Windows 7 + 10 (InDesign CC + CS6) and Mac (InDesign CC)
If you create a Drop Shadow between 19 - 55 mm in size and export the page as PDF-X3 with 300 dpi, the full resolution is not rendered (check with Acrobat Pro DC - Preflight with image resolution check). Under 19 mm and over 55 mm everything is OK. Tested on Windows 7 + 10 (InDesign CC + CS6) and Mac (InDesign CC)