Hi Ukko,
This newsgroup is for people getting started with Microsoft Access
database software, and you may get a better answer in a PowerPoint
group.
For the best quality the image file should have the same pixel
dimensions as when it is actually displayed during the presentation. You
would set the camera for the highest possible pixel size and quality and
then downsize the image as required when creating the presentation.
For non-critical work, if you set the camera to produce a 1024 x 768
image with medium or low JPEG compression the results should usually be
satisfactory.