Thank you. I see the standard process to open the compur shutter. But on the Hugo mayer lens shutter, it attached a adapt ring for quick release the lens elements( about 90 degree to change). The adapt ring attached to the front of the shutter so firmly that I can not remove it. The ring block the three tabs to remove from the slots after I turned the front panel. I can not maintain the shutter without the front panel removed. Any suggestion to me?