Quote Originally Posted by AndreasT View Post
Tungsten, but I use a filter, I think it is a 80c. Would have to check that up. To compensate the colour somewhat.
That should be fine.

So you would use the speed you find at the ISO triangle as a benchmark. And if you start to do different developers/compensating developers etc. Then look how the curves compare to find a new EI. Otherwise take that one speed you found in the first place and use it all the time. Delta-X provides the theory that supports the idea that the effective speed doesn't change a lot with changes in development.