xya, thanks for the reply. Please read the second part of the user manual, which is here: http://www.butkus.org/chinon/polaroi...aroid_mp-4.htm Go to p. 25, which states explicitly that the lens' diaphragm control ring is used to set the aperture.
Originally Posted by xya
The aperture control you pointed out is used to adjust the lens' aperture when the lens is mounted behind the shutter using the Reduction Kit. You'll have to scroll down the document to find this text.
Haste makes waste. Or something.