The DPI of the tiff images exported by PowerPoint seems 96. For posters, larger DPIs like 150 or 300 are needed. Is it possible to change the DPI of tiff images exported by PowerPoint?
In the options of PowerPoint, there is a setting for choosing DPIs. However, it have no effect.
Check the post on changing the DPIs of PowerPoint exported slides images:
How to change the DPI of images exported from PowerPoint slides