For s21 ultra, s22 ultra and s23 ultra where macro shot is available, just get near the subject, very near as long as it can focus on the subject. Just using the main camera.
I can still remember I tried it with Z Fold 4(same camera set up) before but with 3x optical zoom then I just adjust so that I can be near the eye to get a shot.
Don't forget to shine a light (separate phone) on the side to have better view or better natural light so that the iris is very visible.
