I am a professional photographer and need an ultra wide fast zoom for situations where space is limited. This happens more often at weddings than you might think. I always use Canon prime lenses for their excellent sharpness, but I was very impressed with the sharpness across the frame with this 16-35mm lens, even at f/2.8. I'm thrilled to have added it to my Canon lens arsenal, it has helped me capture full length shots in tight spaces where I used to shoot waist high. Just make sure to keep the camera as straight as possible when taking group shots to keep distortion to a minimum. Also great for landscape portraits.