Blurry Photo

I just can’t figure out why images become blurry when I set img_size to large, or use a percentage, or even pixels.

This is my shortcode text:
[handsometestimonial id=”15832″ template=”1″ img_size=”large” img_shadow=”yes” img_round=”yes” txt_align=”” subtitle_italic=”true” subtitle_size=”20px” subtitle_color=”#a30134″ title_color=”#a30134″ title_size=”25px” tst_size=”0px” tst_color=”black” ]

And this is how it looks:
https://screencast.com/t/n1isclP1

I even tried using the original 5MB file. Why can’t it show at least a reasonable higher resolution with img_size set higher?

https://www.ads-software.com/plugins/handsome-testimonials/