90+% of the time when my students show me their cloud pictures, they are exposed wrong. Sad, when it can really be so easy. I am not talking about sunrises, sunsets, colors in the sky. Those wonderful white puffy clouds that can be changing shapes ever minute. The ones where you imagine faces, dragons, elephants. I use a Canon 80D (2 90Ds on preorder) and usually a 70-200mm lens. ISO 200, HTP, 15 point AF, f/8, exp. comp. = 2 clicks to the left (darker.) Each shot will be perfectly exposed. You should concentrate on composition.