Media elements inside slideshow titles can be set to display to either fit the space of the window in their aspect ratio, or they can be set to fill the space full-bleed.
If set to Fit, the image may have space around it to accommodate display of the complete image, and the back and forward arrows appear off to the side of the media element.
If set to Full-bleed, some cropping may occur as the image fills the given display space and the back and forward arrows display on the media element.
Fit example
Notice the white space around the image and the back and forward arrows off the image.
Full-bleed example
Notice the lack of space around image and the back and forward arrows on the image.
The default display is Fit, but the option to change it appears on each slide information page in the Platform.
In order to change the setting, navigate to the slideshow title, and select a slide to modify.
In the slide information pane, there's an Image Display checkbox with options for Fit or Full Bleed.
Make a selection and click the SAVE button at the upper right of the Platform interface.
The changes will go live the next time the Release containing the slideshow is published.
To learn more about slideshow releases, see this document: Title Type - Slideshow