If the *ist DS circuitry is like nearly any other camera I've had
with dedicated flash metering circuitry, as long as the body and
flash are communicating, the flash exposure compensation simply sets
the flash metering's quench signal to the flash unit higher or lower
depending upon how you set it.
So, for instance, if the FEC is set to -0.5EV, the quench signal will
go to the flash when the flash metering sensor records .5EV less than
the nominal normal flash exposure is received.
This is independent of the Exposure Compensation setting for the
ambient light metering because the ambient light meter uses a
different sensor setup. The P-TTL system should use both ambient and
flash sensors, makes its exposure evaluation prior to actual exposure
time. The TTL flash metering operates at exposure time only.
Both the AF330FTZ and AF280T are dedicated units allowing the DS body
to do TTL flash metering so the FEC control is active. They don't
support all the functionality of the body or P-TTL mode, but they
support everything the body can do with respect to their capabilities.
My flash, a Sunpack 383, is not a dedicated unit and has its own,
independent flash metering system. The body knows nothing about it:
the body and lens have to be set manually for shutter speed and
appropriate aperture when using it.
Godfrey
On Feb 5, 2006, at 5:42 PM, Brian Walters wrote:
I'm a bit confused about the flash compensation capabilities of the DS
- not surprising really, even after many years of photography I still
find flash a dark art.
I originally assumed that flash compensation was only available with
the built-in flash. The manual doesn't actually say that but it talks
about flash compensation in the same section as it discusses the
internal flash, so I put 2 and 2 together......
Anyway, after experimenting a bit with compensation using the internal
flash, I attached the AF330FTZ and found that the flash compensation
indicator still appeared in the viewfinder, suggesting that I could
get compensation with the external gun as well. I then attached the
old AF280T and got the same result, which I found surprising.
So, can anyone explain the flash compensation capabilities (or lack
thereof) with external flashguns?
