When inserting an image into a post or generic content widget, the max width attribute only works to a maximum width of 550px.
As an example, the screengrab is 585px wide. When I inserted it into this post I altered the max width to 585px and chose insert, but you will notice that it has been resized to a width of 550px.
I think that this issue is especially important now that the options to alter page layout allow you to have content which spans all columns.
I'm guessing that this 550px upper-limit value is configurable somewhere - can anyone point me in the right direction?