fit/resize image into slideshow

Hi,
if I set the Plugin to

Maximum width: 0
Slideshow’s height: 480
Fit image into slide (Stretch image): No
Shrink slideshow’s height when width shrinks: No

pictures that are to *wide* do not get resized – only part of them is shown.

If I set

Fit image into slide (Stretch image):

to YES, the images in landscape are resized perfectly – but the images in portrait (like a letter) are resizes unproportionally, they are squeezed into the slide (which makes sense, but is not what I want).

If I set

Maximum width: 0
Proportional relationship: 3:1
Fit image into slide (Stretch image): No
Shrink slideshow’s height when width shrinks: Yes

all images get resized correctly/proportinalety, BUT the slideshow is much smaller now, about half the size.

Any idea how I can get the BEHAVIOUR of the last setting in a “forced” size of max 640:480 (on a big screen) – resizing responsively if displayed on a smaller screen (or if window is resized)?

Thanks, Ulrich

https://www.ads-software.com/extend/plugins/slideshow-jquery-image-gallery/