Meet our Diamond Doves! They (& their cage) are helping me out with this test. :) Basically I just turned my desk chair around to shoot these photos.
Shot using ambient light. Only artificial light is from computer monitor approximately 5 feet away from cage. There are two skylights (one right overhead, the other across the room), a sliding glass door (seen in the photo below) and three other windows in the room. However, it is after 4pm here on the East coast & getting darker. The images make the cage & room look much brighter than they are.
50mm lens wide open at f1.4. 3200 ISO
Because of the darkness in the room the lens had a problem focussing on the birds (auto-focus used) and so concentrated on the cage.
28mm lens wide open at f1.8. ISO at 3200 again.
