> "Jansen" <[EMAIL PROTECTED]> wrote: ...
> Exposure is determined by aparture and shutter speed, isn't it?
> I always pointed the middle focusing-point to the face first, recompose, and
> then took the pictures (with the camera's flash). I used P-mode most of the
> time. The pictures with dark/brownish skin colored people always have
> correct exposures; pictures with light/yellowish skin colored people tend to
> be overexposured; on both cases, elan 7e showed the same aparture and
> shutter speed values. Shouldn't the results be the same since every other
> factors are the same (same room, camera, flash, lighting, lens, clothing,
> apparture, shutter speed. The only difference is the skin colors)??
Hi Jansen,
This thread is ON TOPIC for the EOS list (and also the Elan 7E list).
Could the exposure variation be due to an error in the way you were
metering flash exposure?
The exposure from flash is mainly dependant upon the power of the flash,
and which (E)TTL sensor is used. Flash intensity is only indirectly
dependant upon the shutter speed and aperture.
Therefore, if you use only the centre focus point, then recompose, your
Elan 7E will try to meter the flash for a central subject. If you have
recomposed so that the central sensor is not over your main subject,
your flash exposure is likely to be wrong.
There are several ways I can think of to get better flash metering
out of the Canon "AIM" system. These could also help with the flash
problems with the EOS D30 (which does not have CF8=1 to link flash
metering to the focus point).
1) If you like using the centre AF point and you are using ETTL flash,
keep your subject in the centre of the frame (e.g. head and shoulder
portraits). If you have recomposed so that there is no subject in the
centre (e.g. a two person portrait), use FEL with one of the subjects
over the centre sensor BEFORE you recompose.
2) Another way is to deliberately select the AF point so that the
flash will meter correctly WHEN YOU PUSH THE SHUTTER RELEASE BUTTON.
The easiest way is to use ECF, but you can also use AUTO-AF SELECT
or the keypad for manual selection. This works even better if you
use CF8=1 and can be overridden with FEL.
3) Yet another way might be to switch your lens completely to manual
focus. Michael Quack suggested that the ETTL sensor will then not be
biased by the selected AF point, and that flash metering might behave
more predictably.
4) The method for Canon and third-party TTL auto-exposure flash is
different. According to Canon literature, the Elan 7E flash sensor
is a 4 segment sensor that covers the entire frame. If the selected AF
point is on the left, segments 1 and 2 are used for flash metering. If
the selected AF point is on the right, segments 3 and 4 are used. If
you use a central AF point, only segments 2 and 3 are used.
If you can set your flash for TTL metering (e.g. 550EX, or using EZ
flash), you can select which sensors are used by the choice of AF point
(left, right, or central).
5) Failing all else, you can use flash in completely manual mode
and use Guide Number calculations. If your TTL-only flash does not
offer manual power selection (e.g. 420EX, Achiever, etc), this can
be achieved by ISO indexing and manually setting aperture and shutter.
Cheers
Julian Loke
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