Karl Shah-Jenner <shahjen@iinet.net.au> writes: > Greg disgraces himself: Er, was that the attachment? But anyway - thanks! You live and learn. The "US" value though surely wouldn't have been written with an 'f'? The table from 1899 certainly suggests not - it had never occurred to me that there was a time when people had not referred to the aperture size as f/x. It is a pet peeve that using "F8" etc. hides the direct and simple meaning of the aperture, though .... actually I think it's still wrong. What we *should* use is v/x; as I understand Philip Greenspun's article, the Nikon macro system shows what he calls the "true" f/value. But if f=100mm, and the effective diameter of the lens is 12.5mm, this is f/8, *wherever* the lens happens to be. But the effective value for determining exposure doesn't depend on the focal length, it depends on the distance from the film plane (v/n), QED. > 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 Ain't the web wonderful. Haven't done anything today... Brian Chandler ---------------- geo://Sano.Japan.Planet_3 http://imaginatorium.org/
