Dave Yuhas wrote:

Alan -

First of all, thanks for the lucid explanation. If I may, let me ask
one, make that two, more questions to make sure I've got this
right...

1 - With TTL, If I'm photographing a bride in a white dress, and the
dress takes up a major proportion of the frame, I should increase
flash compensation to insure the dress looks white in the final print?

Yes. Depending on the proportion in the image frame, +1 to
+1.5. If the groom (charcoal) and the bride are together, it may
or may not be quite a wash ... it's always hard to outguess the
flash exposure system... incident meter when you can.

note: read your camera manual regarding metering with flash; esp
if you have mixed elements in the scene and you are using only
the center AF spot depsite subject being to the side. On my
Maxxum 9, flash metering is weighted to flash-meter element
corresponding to to the AF selector. You can force scene-average
by holding the DOF preview button (on the Max-9, anyway). A
custom function can also force even weighting.

Assuming negative film and that you may be 'rating' it 2/3 over,
you might want to knock half a stop off the flash comp to
maintain details in the whites.


2 - If I place a diffuser on the flash, flash compensation is not
necessary because TTL will compensate (as long as I'm not pushing the
outer limit of the flash range)?

Precisely so; and to help out (avoid the upper limit) 'give' the
flash another 1.5 stops of aperture if appropriate... about a
wash for a small difuser (if you have an incident flash meter you
can quickly determine how many stops are lost... if you mean a
sto-fen then this factor is a bit variable depending on the room
you're in)

Note, for critical work, and when I have the time, I make flash
incident readings and control the flash manually (5600HS, 5400HS)
which can be done wireless as well as on camera.

Cheers,
Alan

--
--e-meil: there's no such thing as a FreeLunch.--