A large sliding glass door is an excellent location to take a quick portrait because of the flood of natural light. North-facing doors are best because the light is soft and indirect. On this particular impromptu occasion I did not have any additional equipment, although a reflector would have been nice for some fill light on the other side of his face in some of the shots.
These occasions useful in helping to build muscle memory for camera settings on the fly. In retrospect, I should have bumped up the ISO and hastened the shutter speed for more sharpness.