Thanks to everyone who enlightened me on their approaches to extention tube aperture calculations (both via the list and by private E-mail). There are a lot of ways to look at the question but they all converge to about the same answer -- in my case the f/2 lens becomes somewhere around f/4 with the extension tubes that take me close to 1:1 ratio.
I shot a few frames on Elite Chrome 200 slide film so we'll see how the calculation match up to reality in this particular case. - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
