Some themes have a floating main column, that adjusts itself to the width of the browser window, or the device where the page is viewed on. These themes are usually called 'responsive'.
In such WP installations you might wish that (Full Size) photos be automatically adapted to the working space in the main display column.
For this reason, there is the possibility to enter auto in the Photo Albums -> Settings admin page in the Column Width field: Table I-A1.
Alternatively one could enter size="auto" in the shortcode.
To simulate the behaviour of this in the current theme I constructed this page, where you can select a column width.
Apart from some sneeky code to do this, is the contents of this page simply: