| 摘要 |
A camera lens barrel suitable for flash photography, wherein flash guide numbers are marked either on the distance adjusting ring or the diaphragm value adjusting ring, is disclosed. The distance adjusting ring and the diaphragm value adjusting ring are so arranged that the rotational angle of the distance adjusting ring required to increase the distance gradation value by the 2ROOT 2 is equal to the rotational angle of the diaphragm value adjusting ring at that time. A clutch mechanism is mounted in the camera lens barrel and arranged so that the distance adjusting ring and the diaphragm value adjusting ring are coupled together during flash photography. The coupling is such that the distance adjusting ring and the diaphragm value adjusting ring are connected together at a relative angular position corresponding to a flash guide number. The clutch mechanism includes a handle and a clutch member moved by the handle between a distance adjusting ring and diaphragm value adjusting ring coupling position (during flash photography) and a distance adjusting ring and the diaphragm value adjusting ring decoupling position (during normal daylight photography). In addition, a depth of field scale, related to flash guide numbers, is marked on the camera lens barrel in a position such that it is exposed when the clutch member is in its coupling position and hidden when the clutch member is in its decoupling position.
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