A couple of issues here:
Firstly, when we display sidescan imagery in the map view (sidescan mosaic), the resolution is heavily reduced, but is restored during export. This is for performance reasons, as the amount of image data required to display a large sidescan mosaic can be enormous - in the order of gigabytes. For this reason, the resolution limitation in the edit view of sidescan mosaics will remain, and mosaics should be exported as MBTiles and viewed as images to get the full resolution.
It is also true that resolution is somewhat curtailed in the sonar viewer compared to RMv1, which can be noticeable for Humminbird logs in particular as these are generally of a higher resolution than Lowrance logs (more bytes are usually stored per ping for Humminbird, although this varies with the range of the sonar log). We do intend to remove this limitation in a release shortly.
