Instant Cameras

Table 2-7. Typical Photographic Exposure Settings for Fluorescent Indications (Film Speed: ASA 64; Filter: Wratten 2B)

TM-1-1500-335-23 Nondestructive Inspection Methods Manual
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T.O. 33B-1-1 2-90 2.7.6.4.9 Instant Cameras. Instant cameras can be used for photographing indications. There are a few guidelines to be followed: a. The camera should not be hand held due to the long exposures. A steady support, such as a tripod or a camera stand, must be available. Some of the instant cameras do not have a tripod socket and a special mounting clamp or fixture must be used. b. Close-up lens plus a mounting ring or adapter to hold them on the camera lens must be available. The lenses must be capable of providing a focus with camera-to-subject distances of 5 to 24 inches. c. The same filters that are used with conventional films must be used, namely the Wratten 2B or 2E for fluorescent indications and the No. 66 filter for visible dye indications. It is also necessary to place an identical filter over the camera electric eye or exposure meter, when the camera contains an automatic shutter control. d. The lens opening on instant cameras is not usually controllable by the photographer. They are usually small enough to produce a usable area of sharp focus even when using color film. e. Shutter speeds on instant cameras are usually controlled by the electric eye. The shutter will stay open until enough light has entered the camera to make the picture. This feature is very useful in indication photography, since it largely automates the exposure. For fluorescent photography, the "lighten- darken" control should be set one or two marks toward darken. This will produce a picture where the part is apparently dark, but still has a visible outline and the indications are bright. This produces a picture of what is visually seen in the darkened inspection booth. f. Instant color film requires a slightly different technique than other films. When photographing fluorescent indications with 2B and 2E filters, set the built-in meter to one mark lighter than normally recommended. Less exposure will not make the part visible. When developing color pictures of fluorescent indications, develop for two-thirds to three-fourths of the recommended time. Over- developing will result in a general blue background; under developing will produce a reddish-brown background. g. Notes: (1) Tubular (fluorescent) black light sources give less satisfactory instant pictures than high pressure, mercury bulbs. (2) Use as much light as possible. Automatic shutters are not as reliable under low light as in normal light. (3) Exposure times of 10 seconds to 3 minutes can be considered normal. 2.7.6.5 Other Methods for Developing and Recording Indications. a. Video Camera Systems. Readily available hand-held video camera systems with very low light capability are extremely useful for showing penetrant indications. The low light sensitivity allows records of indications to be made without the high light levels and extreme exposure times often required with conventional photographic film methods. Many of the video camera systems are equipped with automatic focusing, exposure, and zoom control. The camera can be hand held or positioned on a tripod. With a hand-held camera, the indication and part can be viewed from a variety of angles. The video tape record is easily viewed on a monitor and can be copied for distribution.

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