Originally posted by Andi Lo Mike, I assume the foil can be taped on the lens instead? I still use my DA lenses quite a bit. Would like to use taks more once I get a 28 and 135 though.
I prefer just sanding black paint off the m42 lens base at the contact location (if the base overlaps the contacts at all.) It can be "repainted" later with a black magic marker if desired.
Most of us short all the contacts but only the 5th from the bottom of the 7 contacts actually need be shorted. I can't think of a reason not to short it permanently, but see no easy way to do it.
It doesn't matter if the window is at the top of the mounted lens. What matters is that the m42 lens base seat flush against the camera's flange surface. That's what insures infinity focus. Because of that, be careful using tape to mount aluminum foil as its thickness might mess up focus at infinity. Aluminum foil is usually only about 5/10,000 inch thick - tapes are typically thicker.
Dave
PS you might consider adding an m42 adapter to each of your taks. That will minimize fooling around when you change lenses. You can do it later when you get more taks.