Kansas University basketball player Tyshawn Taylor, center, texts on his phone during NCAA Final Four events last spring. In this dimly lit image, I had reached my largest aperture of f2.8 and my hand-holdable limit of a 1/25th shutter speed. My only choice was to increase my ISO to 5000. I was willing to accept a decrease in image quality just to obtain the photograph. Being aware of what ISO you are using can keep you from experiencing unintended loss of quality in your photos.