Image with full width

Hi,

I read the forum and found some nice ideas but one is missing. I like one feature of another theme (Ness) but I prefer this one ??
I’m using the WP tiled gallery with jetpack which is nice but I’d like to know if it is possible to set a class on an image to tell it to take the full width of the “article” class. It seems, this part is responsive and the default width 771px, and I’d like to increase the width. I tried a solution told by Ben

.entry-content img {
  position: relative;
  left: -150px;
  max-width: calc(100% + 300px);
}

but when resizing, it does outbounds of the article block which is not nice to see. I just want an image to take the full width, only of the white box.

thanks in advance.

btw, I love the theme AND my readers too!

I’m not sure to be clear :/