[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,


!!!! This is very confusing. Why do they call the filter factor 2 if it's really 1.4?

--shannon


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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