Based on Dewey's theory of art, aesthetics, and experiences and photographer Barnbaums' writing about expanded perception through photography, we conducted a one-day experimental mathematics education unit. Using photography in outdoor conditions had a positive impact on teacher students' perception of the use of photography for teaching mathematics. To study the changes in students' visual attention deeper, we used gaze-tracking to analyse one student's visual attention when walking outdoors after the activity. The gaze data indicated that more visual attention was given to objects he had photographed or discussed during the group activity in comparison to other objects.