Originally posted by vicentesagredo I still dont get it...the lens would be wide open when I mount it on camera, so focusing and framing will be wide open?
but the shot will be with the aperture selected in the aperture ring?
if that is, its exactly what i was looking for
Actually, unless you always shoot at the widest aperture (meaning the narrowest depth of field), it doesn't matter if the lens is an M, A, F, FA or DA series. The camera body has no way of knowing what your lens aperture is set at when it meters the scene. My mod will provide the lens information to the camera body and allow you to use a variety of the camera's exposure modes.
You should still do a test shot to check exposure. Apparently M lenses (anything prior to the A series) require a slightly different amount of motion of the lens' stop down lever to reach specific f/stop values. You will never underexpose, but depending on the lens and selected aperture there is a risk of over exposure. Fortunately, unless you blow out the highlights, moderate over exposure can often be fixed in post processing.
I've done the 'A' contact plug on the body and applying the extension tube insulation patches often enough, I can do the whole job in less than 15 minutes. My only tools are a small phillips screwdriver, a bit of aluminum foil, a pair of scissors and magictape. And you can reverse everything in a bit over 5 minutes - although I don't know why you would want to do that routinely.