What is Vari-Angle Prism? Canon's optical image stabiliser uses the Vari-Angle Prism to compensate for image shaking. The Vari-Angle Prism is composed of two pieces of flat glass joined by a flexible bellow made of a special film that can expand and contract as required. The space between the glass plates is filled with a liquid of a high refractive index. The liquid is silicon-based oil specially developed by Canon. One glass rotates for pitch movement and the other for the yaw movement. Therefore, expansion and contraction of the flexible bellows can vary the top angle.