Laser damage threshold, wavefront distortion, and mounting stress are the three most common sources of beam splitter failure or underperformance in real optical systems. The set up is either: Camera lens - beam splitter - camera x2 Or, Beam splitter - (lens + camera) x2 I want to be able to take 2x photos at once, so the light has to go through the beam splitter. I used the polarised flexible sheet as a proof on concept, which worked but need to make it more. Quick-reference for beam splitter types, Fresnel equations, polarizing designs, and selection workflow. See the Comprehensive Guide for worked examples, SVG diagrams, and full references. This article and its illustrations will go a long way toward making the correct choice less of a risk. All curves show typical performance.