Ibso
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The Ibso shutter with a 3 blade diaphragm was made by Gauthier from 1908-1926. It was the first everset shutter (i.e. an 'automatic' shutter, not needing to be cocked) on the market.[1] The cylinder at the top of the shutter is a pneumatic air-brake which regulates the speed. The shutter is found on many folding cameras of the period and has the usual limitation of everset shutters that it cannot offer very fast speeds; the original Ibso shutter gives seven speeds from 1 to 1/100 second, plus 'B' and 'T' and was provided with a cable release socket. There are also Ibso shutter variants that offer an extra speed of 1/150 sec.
Gauthier replaced the Ibso shutter with the Ibsor.
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