I give up. Please check my website: http://www.bobkiss.com/ "Live as if you are going to die tomorrow. Learn as if you are going to live forever". Mahatma Gandhi -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx]On Behalf Of BertS Sent: Tuesday, October 03, 2006 11:03 AM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: estimating filter factor: gray card? BOB KISS wrote: > The relationship between f stops and factor is NOT a square root. As > demonstrated in my previous e-mail: " the square root of a factor of 8 is > 2.8 but we all know that a factor of 8 equals exactly 3 stops (2X2X2)." > The relationship is exponential factors of 2 NOT the square root which is > ONE SPECIFIC exponential factor of 2. > Therefore it DOES happen to correspond to the square root in some SPECIFIC > cases but not all. > CHEERS! > BOB > The relationship between f-stops and filter factor is a square root. Just divide the metered f-stop by the square root of the filter factor and you will get the f-stop. If you meter a scene and the meter indicates that f/16 is the correct exposure and then you put a filter with a filter factor of 8 then the correct f-stop is f/5.6. 5.6 is 16 divided by square root of 8 (2.8). If you change the filter to one that has a filter factor of 4 then the correct exposure is f/8. 8 is 16 divided by square root of 4 (2). ============================================================================ ================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.