Filter stop adujustments

[RuggerJoe]

Does anyone know if there is some place I can find how mutch I have to adjust my exposure by for a given filter? For instance a #47 and #58.

[Mark_Cohran]

Can you provide a little more information? For DSLR's you don't have to adjust exposure since the filter goes over lens and the light entering the camera metering system is already filtered....pretty much the same with most modern P&S cameras. Are you talking about for an incident light reading? Additionally, what do you mean by #47 and #58.

Mark

[Doug Pardee]

As Mark said, if you're using the in-camera metering it's already looking through the filter so you don't need to do much. There might be some color-sensitivity issues in the metering system, but you'd have to address those experimentally.

If you're calculating exposure using something other than the TTL metering system, then of course you do need to apply the filter factor. Many filters have the filter factor marked on the edge of the filter.

Filter factors vary depending on the lighting conditions, filter manufacturer, and the imaging medium. The Wratten #47 and #58 filters are color-separation filters, usually used with B&W film. In daylight conditions on T-Max film, a Kodak #47 has a filter factor of 8 (3 stops), while a Kodak #58 has a filter factor of 6 (2-2/3 stops). Under Tungsten lighting on T-Max, the Kodak #47 filter has a filter factor of 25 (4-2/3 stops) and the Kodak #58 has a filter factor of 6 (2-2/3 stops).

I'm not clear on why you'd want to use these filters on a DSLR, as you can do color separations in post-processing quite easily.

[Mark_Cohran]

Originally Posted by Doug Pardee

Filter factors vary depending on the lighting conditions, filter manufacturer, and the imaging medium. The Wratten #47 and #58 filters are color-separation filters, usually used with B&W film. In daylight conditions on T-Max film, a Kodak #47 has a filter factor of 8 (3 stops), while a Kodak #58 has a filter factor of 6 (2-2/3 stops). Under Tungsten lighting on T-Max, the Kodak #47 filter has a filter factor of 25 (4-2/3 stops) and the Kodak #58 has a filter factor of 6 (2-2/3 stops).

I'm not clear on why you'd want to use these filters on a DSLR, as you can do color separations in post-processing quite easily.

Thanks, Doug. I didn't even consider that he was referring to Wratten filters.

Mark