Grid Image Size v8.9

What’s the optimal size of images being displayed on Grid view on homepage?

I have played around with lots of image size options and the image will look distorted depending on what view you’re in (e.g. responsive, full width, etc).

For example, I am using image size 350×185 which looks fine on the homepage, but in a responsive environment (i.e. tablet machine), the image height shrinks and shows a grey space. If i use CSS to fix the height then the image looks distorted.

REFER TO ATTACHED IMAGES.