Philip Forrest Posted October 20, 2019 Share Posted October 20, 2019 With regard to lenses that have a stated T stop but also are fitted with a reflex viewfinder, what should be a corrective factor to account for the prism that is sitting within the optical path? I've seen lenses of the same type, one with, one without a reflex finder and haven't seen any mention of a T stop correction, ie Angenieux12-120. Thanks for answering this curiosity of mine. Phil Forrest Link to comment Share on other sites More sharing options...
Premium Member Dom Jaeger Posted October 22, 2019 Premium Member Share Posted October 22, 2019 I believe the reflex "dog leg" version of Angenieux's 12-120 is marked as T2.8 rather than the T2.5 of a standard version. The iris scale ring on those zooms is usually marked in white f/stops on one side and red T stops on the other. A normal 12-120 is f/2.2 and T2.5, so the lens itself loses a third of a stop in transmission. The reflex version loses another third of a stop to the finder, to become T2.8 Link to comment Share on other sites More sharing options...
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