In a photography method, a partial vacuum is provided within a pressure housing of a camera having an unexposed film unit. The camera is sealed against both air entry and venting, while in the partial vacuum. The camera is kept sealed until the film unit is fully exposed and while sealed, a relative pressure differential between the interior of the camera and an environment external to the camera is continuous indicated. The camera has a housing having an internal cavity water-tightly sealed from the external environment. The internal cavity has an unsubmerged internal pressure, at room temperature, less than air pressure at sea level. The camera has a camera frame assembly disposed in the internal cavity and a seal integrity indicator that provides the continuous indication of the relative pressure differential.