t vs f stop
Posted 20 August 2007 - 05:16 PM
my name is elie and i'm a student filmmaker. this is my first post so take it easy on me...hehehe
well this is a very classical and FAQ for which i haven't got any convencing answer yet.
if T stop is more accurate than F stop then why use a light meter and not a spot meter all the time?
and if my question is not very accurate would you please explain to me "in a convincing way" the difference between Mrs T and Mrs F?...
thanks a lot
Posted 20 August 2007 - 07:24 PM
An f-stop is a physical size, the number determined by a ratio between the length of the lens and the size of the aperture. A T-stop is just an f-stop mark that has been shifted over on the barrel to compensate for any light lost as the light passes through the lens. In other words, for example, they measure the amount of light coming through the aperture that should be f/2.8 on their meter, but find it is one-third of a stop less than that, so they move the marking for "f/2.8" on the barrel so that you actually get f/2.8 out of the back end of the lens. But having adjusted the position of the f-stop mark, they can't really call it an f-stop anymore, so they call it a T-stop ("transmission" stop.)
So if your meter tells you to shoot at f/2.8, if you set the lens to T/2.8, then you'll get f/2.8 in terms of exposure. If your lens did not have T-stops, then f/2.8 on the lens may actually be slightly less in terms of exposure.
Posted 26 August 2007 - 06:09 PM
Posted 03 September 2007 - 02:34 AM