It left perforations in it similar to tiny pinholes. The oldest "lenses", pinholes, used in pinhole cameras, keep perspective accurately. For example, in optics pinholes are used as apertures to select certain rays of light. Similar holes made by other means are also often called pinholes. This results in a weld with pinholes, which is weaker than a typical weld. A decrease in permeability indicates tighter packing and could lead to blows and pinholes. After 1930 he chose to continue his experiments with pinholes replacing the lenticular screen. The surface of the table has a series of small pinholes drilled in it. R. Levi developed tools for these measurements, essentially pinholes and the camera obscura. The scattered light is detected by a photo-multiplier after passing through two pinholes. This leaves tiny, but unacceptable, pinholes in anything printed from the roll in the future. Pinholes (homemade or commercial) can be used in place of the lens on an SLR. Reptiles also have eyes the size of pinholes or protected by valves. Later vacuum-chamber experiments suggested that the unwinding of the reel uncovered pinholes in the insulation. By adding pinholes, light throughput and thus sensitivity are increased.