[LargeFormat] Re: flash exposure

[philip Lambert]

How does one achieve correct flash exposure?  I bought an old Canon flash at
a fair without a manual and ran off several exposures of Fuji colour
negative film of an Xmas arrangement of bottles of alcohol standing on brown
wood furniture against a white wall, at various apertures, with the camera
on a tripod at a fixed distance.  The only differences I noticed in the
prints were that the least bright objects, the furniture, improved in colour
as exposure increased.  The negatives became denser, but the light-coloured
objects looked much the same in all the prints.  I am inclined therefore to
give generous flash exposure for negative film but what would readers advise
for transparency film? Is a good flash meter the answer?
As a separate matter, my Nikon F90 and SB22 seem to automatically
underexpose slightly (using TTL flash metering) so I usually give plus half
a stop. Do I have a defective outfit or is a half-stop adjustment regarded
as insignificant? Or are the manufacturers' claimed film speeds only an
approximation?
Philip Lambert