What I do is remove both the front and rear element sets. Then I set the shutter to bulb and keep a cable release locked in order to keep the shutter blades open. Then carefully, using a clean soft tissue with a drop or two of lighter fluid, I gently wipe the aperture blades at all the different size openings, both front and rear. There is a surprisingly small amount of oil needed to hinder these blades' quick movement, as the tension is caused by only a simple wire spring.
Sometimes there is oil in the shutter blades as well. I know that this sounds 'disastrous' but you can insert a pencil in the open aperture and then release the shutter blades by unlocking the cable release. With the pencil there the shutter blades will not fully close and will 'expose' the places where there is a tiny bit of oil (to wipe clean). Just be careful and force nothing. After wiped clean simply remove the pencil.
Oil on these blades is usually caused by the camera having been in a very hot environment (glove compartment during summer) for even a few hours. The oil from the helical can slowly merge with the rest of the lens's mechanics, including the aperture blades. - David Lyga
Last edited by David Lyga; 09-28-2012 at 07:48 AM. Click to view previous post history.