Having read this thread and the Mortenson article on unblinking eye, one question stands out for me. Could this be one path to one of my holy grails of shooting available light, handheld, with my graflex in the EV range of what would be 4-8 at iso100 using a shutter speed no slower than 1/30. With my 4.5 lens, that means that I need an effective film speed of around 250 at the high end, but at the darker end, I'd calculate I'd need a probably unachievable exposure index of 8000.

Given the absence of LF film >iso400, would it be reasonable to say that the Mortensen method might be one way to find out what my greatest working exposure index between 240 and 8000 might be? Is the goal with this method to develop the film as long as possible until just before you get to an unacceptable level of base + fog?

I do development by inspection fairly often, but I haven't the slightest idea how one judges b+f before the film is cleared. This leads me to believe that maybe a series of time/temp tests are in order to establish a baseline, after which DBI is used for routine development to know just when to pull a given neg. Am I on track so far?

I figure I could shoot a stack of 4x5s of a 21-step wedge on a light table, putting zone V at step 11 at ei 800 or so, then cold/stand processing it as described, pulling a sheet about once every half hour starting at one hour and comparing the b+f of all of them once they're dry. A little challenging to do without an actual densitometer, but this might also be my excuse to get the method of substituting a spot meter down.

Does this sound like anywhere near an adequate way of determining what my maximum speed would be with Mortensen method would be?

Final question (for this post, anyway) -- what kind of film would likely yield a higher effective speed: the one with the highest ISO rating, or the one with the lowest base + fog?