--- James McCauley <[EMAIL PROTECTED]> wrote:
> Forgive me if I'm missing something obvious, but
> if it's accepted that
> there is a formula for producing a correct flash
> exposure (e.g. ISO rating
> + subject distance = X amount of light for correct
> exposure) couldn't the
> flash calculation simply be linked to the lens'
> focus distance so that
> whatever you focus on is correctly exposed, rather
> than relying on the
> amount of light coming back into the lens. This
> would cure another problem I
> suffer with, subjects wearing bright reflective
> clothes. The user could then
> dial in any under or over flash requirements.
> I appreciate it's obviously not as simple as
> that, so could someone let
> me know where my arguement falls down. Also, any
> tips on flash exposures
> welcome.
It falls down simply because it doesn't account for
the varying reflectivity of different subjects. A
black man in a white shirt, for example, could end up
with the shirt overexposed and the skin tone
underexposed.
In the best of cercumstances, the ETTL system accounts
for this quite well. And Chuck Westfall has told me
that, at least with the EOS 3, the E-TTL system WILL
use distance information in the calculation, but only
if the exposure calculated by the flash meter seems
way off. I do, in fact, find my flash exposures with
the 550/EOS combo to be quite good, most of the time.
But it seems more and more clear that Canon cut
corners in a few places in the D-30. It's a great
camera for some uses, crippled in other situations by
poor AF and flash subsystems.
=====
Bob Meyer
Life is uncertain. Eat dessert first.
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