[pure-silver] Re: estimating filter factor: gray card?

 
 
In a message dated 9/30/2006 7:35:49 P.M. Eastern Daylight Time,  
sstoney@xxxxxxx writes:



"As I understand it, if the filter factor is 2X, you open up a  full stop," 
or you double the exposure time.  So, opening up a  third of a stop would be 
the same as multiplying the time by 1.3. For example:  let's say the exposure 
at 
f/64 should be 6 seconds, without the filter. With  the filter, it would be 8 
seconds, or 6 times 1.33 



Shannon,
 
No, if the filter factor is 2 x you would open 1.41 stop not 1,  
approximately half a stop difference.  You could also adjust the time by  1.41, 
giving you 
8.46 seconds.  Either way you have a fractional leftover  that I would just 
round up giving an exposure of f-32 1/2 and leave the  time at 6-s.
 
Ralph is probably 'more' right but I don't understand what he is saying  
(that's my problem, not his.).
 
Bruce  Osgood
Camclicker @ aol.com
Brooklyn,  NY.

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