Re: question about ISO vs EI

[Ben Kreunen <ben@xxxxxxxxxxxxxxxxxxxxxxx>]

At 10:50 PM 10/17/2000 -0600, you wrote:
>But Ben, what I don't get is why would your speed go UP when you meter with
>a filter on?

Your film speed doesn't change, the setting on the light meter does to 
compensate for the fact that it is receiving less light and reporting 
longer shutter speeds.

Personally I don't bother reading filter factors.  Since I normally meter 
without a filter (because the camera I use to shoot IR doesn't have a light 
meter). If I do need to meter through a filter I just meter a scene first 
without the filter, noting the shutter speed... then put the filter on the 
lens and meter again, changing the film speed until the shutter speed 
matches my first reading.  That way you get a "filter factor" that is 
suited to your camera's light meter.

Cheers

Ben

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