Thanks Karl. I'd lost the bookmark to that site and have been feverishly trying to find the page since Brian asked his question. I had hoped to redeem myself somewhat before you stepped in with the answer I knew you had. Greg > -----Original Message----- > From: Karl Shah-Jenner [mailto:shahjen@iinet.net.au] > The 'US system' is the 'Uniform System' - an early aperture > 'standard'.. > At that same time 'Intensity Ratios', were evolving and would > later become > the f-stops we know today (intensity ratio being the ratio of > the focal > length to the size of the aperture) > > > you can find more at: > http://www.ai.sri.com/~luong/photography/lf/shutters.html > > > karl >
