Common skin warts (also called cutaneous warts) are raised round or oval growths. A wart may be lighter or darker than the skin around it. Some warts may have tiny black dots in them, often called seeds. The dots are small, clotted blood vessels. Warts may occur alone or in larger groups that merge and form patches.
According to Canon (link):  Canon addressed the âfeedback loopâ in later model IS lenses by introducing an algorithm to the IS detection system to automatically recognise when the lens is mounted to a tripod.
The most popular type of tripod head for large birding lenses is, by far, the gimbal head. A gimbal head works like a see-saw: it maintains a fine balance on the lens, so that very moderate forces applied to one end (the camera end) are able to precisely control movement of the other end (the objective lens end).