My favorite test object, as it's allways at hand. Seen from my bedroom window is a column of traffic light reflectors lighting big multilevel crossing. Estimated distance 500 meters (1500 feet). This one shot with Sigma 50-500 and Sigma 2x teleconverter added. Whole apparatus laying on pillow (!) that is just put on the window frame. No resizing and no post processing done, except for cropping. In-camera sharpening set at "normal". Compare it to the pic on the right, which was shot without teleconverter.