Wayne,
I've seen merciful's work, too. Or at least that one image. And my first, honest response is - I don't know the exact shooting conditions, metering pattern or method used.
ALSO - there is a difference between getting acceptable (and perhaps extraordinary) results when pushing like mad, and actual film speed. One must basically remember this whenever one reads my posts 🙂.
For instance, let's assume merciful metered and shot such that he was actually using an EI of 12,800. Which he probably did not - he probably set his meter to 12,800 and shot away. Doesn't really matter. It was a crazy push.
What actually happened is that his dev technique led to proper midtones with an acceptable (and actually amazing) control of highlights. That's the definition of pushing - you pull the midtones up at the cost of highlights. It's just that he really, really controlled those highlights through the use of serious compensation.
HOWEVER...the numbers I've been giving Stephanie are actual film speed based on shadow density. The shot that merciful showed didn't have areas of significant shadow area that required density - it actually was a fairly low contrast shot (as in everything was close to the same tone, not that the image was flat. But the neg was flat). But if you are concerned about sufficient density in shadow areas, then TXT has a speed of about 250 in Rodinal 1+50. Because it's so old, you'll need to add at least 2 stops exposure to get the same shadow density over base fog, meaning shooting at 80 or so.
HOWEVER^2, perhaps getting that amount of density in the shadow area isn't important to you (general "you," not specifically you, Wayne). In which case you have a lot more flexibility.
As I said, I almost always speak in terms of film speed in terms of density in shadow areas, which is a very Zone System style definition. I deviate from that only if I explicitly talk about pushing.
allan
