Well I'm just starting out with this film, and got hold of the response
curve of from the Fuji website.  If I know where 18% grey lies on the
response curve, I can adjust the esposure to place the metered tonal range
wherever I like on the curve - so if I meter from highlights, I know to
increase the exposure by x stops.  I know there are some general rules of
thumb for slide film, but I thought it'd be nice to precisely work it out
for myself.

Thanks in advance.

Duncan.

Actually, I've just found out the anwser for myself from googling "ISO
5800:1987" and then trudging through this article...

www.largeformatphotography.info/ articles/conrad-meter-cal.pdf

(which is very good by the way).

I seems like Slide Film ISO is defined by...  ISO = 10/(midtone exposure in
lux-seconds).  Therefore midtone exposure is 0.1 lux seconds for this ISO.
This relates to Zone V metered exposure by -0.14 stops for Canon and Nikon
cameras, and by 0 stops for Pentax and Minolta cameras (due to differences
in metering).  You can then look at the response curve of the Fuji film
(pdfs are on fuji's website) to see that this exposure gives a density (for
pentax) of 1.0 on their scale (arbitrary units, I think).  You can then
visually see on the graph that Zones VIII is right at the toe of the curve
and zone III at the shoulder.  In effect Zone VII should be used for
highlights where there will some loss of detail (two stops above metered
value).  Basically you have a range of 5 stops with some loss of detail,
more like 4 stops if you want to keep all the detail.  4 stops means +1 for
highlights, metered value for medium grey, and -1 and -2 for shadows.

I'll now approach Fuji Sensia 100 with this armoury of knowledge (and
probably fail miserably)!

Duncan.