If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. 


Thread Tools  Display Modes 
#1




fstop to light transmission % ratio question
"Tom Gardner" wrote in message gy.com... Is there an easy formula to translate fstops to the percentage of light transmission? As each stop is 50% of the previous stop, where did the numbers come from? Transmission of light is not associated to f/stops, that is a function of the lens characteristics, but, I think you mean how much light "X" aperture ALLOWS compared to a "Y" aperture. If so, the formula is ( X^2 / Y^2) * 100 for instance, comparing f/32 with f/4 (32^2 / 4^2) * 100 = ( 1024 / 16 ) * 100 = 6400% f/4 allows 6400% more light than f/32 The other way around: (4^2 / 32^2) * 100 = 1.5625% f/32 allows just 1.5625% of the light f/4 allows Where it comes from?: it seems to have come from hell, for those that forgot their 6th or 7th grade math! :) Guillermo 
#2




fstop to light transmission % ratio question
Hi Tom,
Saying what the other posters have said in other terms, if you open up a lens from say f/2.8 to f/2, you are increasing the radius of the aperture circle by a ratio of 1.414, thus doubling the square area of the aperture circle, thus allowing twice as much light to pass through in a given amount of time. Francis A. Miniter Tom Gardner wrote: Is there an easy formula to translate fstops to the percentage of light transmission? As each stop is 50% of the previous stop, where did the numbers come from? 
Thread Tools  
Display Modes  

