Terry, the entire front of the lens unscrews as a unit with all front elements included. Simply grab the front of the lens with your hand and unscrew it, it probably isn't even very tight. I'll get a photo if that would help. Once the front is unscrewed you have plenty of access to the diaphragm leaves, but it might take an hour or more of repeated wiping with lighter fluid to get them clean enough to work freely. Let the lens dry over night before screwing the front back on.