Quote Originally Posted by 2F/2F View Post
Umm, for fluorescent it is about one stop, but not for tungsten. Correcting for household tungsten bulbs requires an 80A and an 81B together, and opening up 2-2/3 stops from the metered exposure.
Dang, I was wrong about somthing again. Memory is so fallible.

You are absolutely right, I normally use an 80a which needs a two stop correction.

I haven't added the 81b, that's something I might have to try but a little tungsten ambiance isn't bad either.

The basic thought that I was trying to get across is that in non-standard light, for example tungsten, exposing the blue layer of a daylight film enough to be able to correct well at the enlarger requires roughly the same change of exposure with or without a filter.

The advantage of using the filter is that the other layers will not be over exposed, relatively speaking.