Reciprocity Timer App I decided to follow the recommendations from this app to see how accurate it was based on my current scenario. Scenario: White Flower in vase, lit by one tungsten lamp placed to the right. Incident exposure reading indicated 8 seconds @ f/45 Bellows was extended by 270mm Film used was Fomapan 100 5x4 sheet film As we can see, the app indicated that I would need a total exposure of 5 minutes and 55 seconds. My gut feeling was that seemed to be a long time but nevertheless, this is what the app indicated so I went for it. The negative came out very dense, almost all the detail in white flower was hardly visible. My only conclusion is that the app calculations for reciprocity must be based on daylight and not artificial tungsten lighting. Am I right in assuming that these reciprocity charts are based around daylight conditions.