First check if you're using the Retina creation setting when creating the .dink file
General Options -> Aspect Ratio + Resolution
If you're creating using Retina setting, and still the resolution of the images is not razorsharp on the tablet, then there is a hidden setting in Powerpoint saving images at low resolution.
You can change this setting by diving into the Registry of you PC. It's not a very common thing to do, but this article from Microsoft shows exactly how to do this: https://support.
For a tablet screen, 264 (dpi) is recommended.
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