Single images in tagdiv composer won´t remain proportions

I have an issue with Single Images in Pages using TagDiv Composer.

If i add a picture that is, let´s say, 1000x200px it looks ok in fullscreen on a computer. However if I reduce the brower window (or look at the page through a mobile device) the image changes its proportions. I understand that this in some cases is a great feature. However it´s not really how I want pictures to behave.

What I want to do is to have the picture keep its ratio (say for example 16:9) and only be resized, NOT rescaled and cropped within a border. I have played around with the options for the image (keep height etc.) but can´t get it to work. Setting a specifiec height also doesn´t help since 200px looks very different on a desktop vs. a mobile screen.

I want the single image to behave like images does when i insert them in a post through the standard wordpress-library function. I must just be missing some setting right? 🙂