This form of control applies to most recent images.
After clicking* on an image to enlarge it, a click* in a particular region of the enlarged image can be used to step to the next or previous image in a group, start or stop an automatic slide show and return.
A group is typically the images in a post or page but a post or page may have multiple groups.
The position of the click* to start an automatic slide show determines the speed of the slide show (currently from a 2 second interval for a click* on the left hand side to a 6 second interval for a click* on the right hand side).
Currently the size of an enlarged image takes no account of the device the image is to be displayed on (the image will be displayed correctly but the image sent may be much larger than required and the resizing may be poor).
The example image is from the Wimbledon page.
* click or touch equivalent but not touchmove.