mc_vancouver
09-19-2006, 11:50
I was curious, recently, about where my 35/1.7 stood in the regular scale of f/stops: 1.2, 1.4, 2.0, 2.8 and so on. And so looked it up. One chart (http://www.uscoles.com/thirdstops.pdf)divides up the range into third-stops, and 1.7 falls midway between 1.4 and 2.0, thus a half-stop faster than a 2.0 lens.
Matthew Cole, who wrote that chart, also wrote this (http://www.uscoles.com/fstop.htm) which is a good, not too technical discussion.
The thing to remember is that each of the exposure variables is directly related to the other variables: one stop on the lens is equivalent to one faster or slower shutter speed, is equivalent to a doubling or halving of the ISO rating. Push a film from ISO 100 to 200, underexpose by one stop, choose one faster shutter speed, its the same thing. Not that I'm suggesting doing all three...at the same time.
Matthew Cole, who wrote that chart, also wrote this (http://www.uscoles.com/fstop.htm) which is a good, not too technical discussion.
The thing to remember is that each of the exposure variables is directly related to the other variables: one stop on the lens is equivalent to one faster or slower shutter speed, is equivalent to a doubling or halving of the ISO rating. Push a film from ISO 100 to 200, underexpose by one stop, choose one faster shutter speed, its the same thing. Not that I'm suggesting doing all three...at the same time.