Brian C.W. wrote:
I have a question regarding my SB-28 and some images coming out w/very
dark backgrounds. As I understand it the 28 has 4 modes TTL w/Balanced fill
flash, TTL, A, and M mode. In TTL Balanced fill Flash I understand the flash
is attempting to mimic ambient light. This is fine when there is some to
adequate ambient light. However when it is dark, specially in the background
the flash seems to be shutting down too soon. The subject is well lit
(perhaps a little dark sometimes) but the background is dark to black
On the LCD panel the TTL w/the little pic of "cross hairs" means
Balanced fill flash, correct? If I switch to A mode and set the Aperture I
get good to great results depending on how long I compose the shot and think
it through. But inevitably there is the time I just want to shoot now and
get a good pic. If I set the flash mode to TTL but w/out the little "cross
hairs" icon does that operate the strobe in non fill flash mode?
Thank you for any and all help Brian C.W.
Brian
In the balanced flash fill mode the camera sends out pre flashes.
These pre flashes are received back by the camera and then the camera tries
to determine what area of the matrix the subject is. By getting reflectance
from the subject in the forground and very little from the background the
camera sumizes that the exposure priority should be for the forground
subject. The camera then uses shutter speeds between 1/30 to 1/250 of a sec
to balance using ambient light. (F90x)
This compares to a standard TTL setup used in othe brands of camera where
the flash will try to expose for an average of the scene and hence give a
better exposure for the background and totally over expose the subject.
Balanced fill flash also underexposes by 2/3 of a stop as in a fill flash
situation it should not be the dominant light souce.
Your choices are to
1/ use std TTL and risk over exposure of the subject
2/ try balance fill but dial in some exp compensation or trick it by
changing the Din/ASA
3/ Change to rear curtain sync as the the priority exp is the ambient
light and the flash fires last as a fill in. This way the background will
be correctly exposed, but in very low light you need a tripod or a very
steady hand
Brian
PS it is very hard for a light source origionating from the camera to expose
correctly for subject and background, if the subject is 1 metre away and the
backgound is only 2 metres away then the backroung recives on 1/4 of the
light intensity of the subject. As the background distance increases so the
intensity drops off.
