... , ±3D, ±4D, ±6D, ±8D, ±10D, ±15D, ±20D.5. Aperture wheel: red-free filter, Large spot, small spot, hemispot.Technical Specification:Name of ... aperture Dimension of aperture Dimension of Image Angle of viewRed-free filter F2.4 F2.3 7°4424Large spot F2.4 ... : 0D, ±1D, ±2D, ±3D, ±4D, ±6D, ±8D, ±10D, ±15D, ±20DAperture: red-free filter, Large spot, small spot, hemispotRated voltage: AA alkaline or ...