Originally posted by BruceBanner I appreciate the replies, but I fear I have asked something that is beyond my technical ability. I need pictures, steps by step instructions
I guess it's exactly like most Pentax PK mount lenses. I think you can find YouTube videos, and a step by step guide in the right section of the Lenses subforum.
You can either remove/unlatch the spring (that's what keeps the iris open), or give up the AV and just use the DOF preview switch (that allows to preview the picture in the same conditions it will be impressed on the sensor, but you still need to work in M).
Unfortunately not all cameras have this function.
If you glue the ring you'd still have the lens wide open, and no AV mode...
Another option would be to imitate the functions of a PKA lens with conductive painting or adhesive copper foil.
As you've already been told, the exposure will be off the more you stop down... and it's an exercise in patience and precision. Not easier than removing the spring, IMHO.
The only advantage is that you can't mess with the innards of the lens, and it's not difficult to reverse to its original state.
If you open the back of your lens, use the right size/type of screwdriver.
If you hate the Green button just forget about it, stop down one click, set AV, and compensate with the +/- function.
F/2.5 to f/2.8 is one third of a stop, I'd forget about it and just shoot.
If you stop down a little more, compensate accordingly. I usually go for the green button once or twice a session, and compensate when needed with the ISO setting. Raw files can often be saved in PP even when I forget the green button procedure when illumination levels change a lot.