I have been looking for an intermediate telephoto zoom lens to add to my lens arsenal. I have owned the Canon 100-400mm lens for a while now but I have never been happy with its sharpness or overall performance and the push pull mechanism for zooming was not very smooth and made tracking while zooming difficult. I was looking at 70-200mm f/2.8 lenses but I felt that I wanted a bit more reach for an intermediate telephoto zoom lens. Someone suggested that I try out the Sigma 120-300 f/2.8 and it looked to be a great idea as it fit nicely in my lens lineup between my wide angle lenses that ranged up to 128mm and my super telephoto Sigma 300-800mm f/5.6 lens.
I never imagined that choosing the “right” ISO for wildlife photography would be the most controversial subject that I would teach. If you ask many pros about which ISO you should use, the most frequent response you will get is: “Choose an ISO based on what you are shooting”. If you are shooting a portrait of a bird or animal, choose a low ISO and when shooting action, select a higher ISO.