Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 170
to a large extent overci by various devices. In the first place it was desirable toincrease the angle subtended by thecondenser by the source. It was. how-ever, found impracticable to make apiano-condenser of suffh iently short focus,as the thickness of glas-: and curvaturewould be excessive,…
Lighting
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