I want to know why the quality of the images in the slideshow are poor.

To change the image quality you need to go to this file
administrator >> components >> comnivosliderpro >> unitejoomla >> image_view.class.php

and change line 30
private $jpg_quality = 81;

try changing the quality to 90 first and c if u like it.

The lower the number the more optimized the image will be for fast upload .