Hi Nikon-aholics,

Happy new-year to all.

Just back from holidays and catching up on a BIG pile of digests.  I noted this
entry and didn't see a response by v4.194, so here goes.

Holger, the overexposed objects in the foreground can have a couple of causes,

1.     If the object is small, relative to the frame, the flash will be trying
to make the whole picture brighter, thus the small objects get overexposed.  How
was the rest of the picture exposed?
2.     If the overexposed object is the subject and is the major component of
the picture it becomes a bit more difficult.

For some reason Nikon have made the close-up program on the F50/F70/F90 cameras
open up the lens (small f-number) to give as little depth of field as possible.
In the majority of cases this is opposite to what is needed.  For the depth of
field needed to have an object which is close to the lens in focus you need to
stop down (larger f-number).

This then has a bearing on the flash.  While the flash is TTL controlled, it
does have limitations.  For an object which is close to the lens you need to
stop down to have the TTL  system quench the flash fast enough.  Basically
during a flash photograph the following happens;

Shutter opens
Flash fires
TTL meter reads the light reflected off the film, when sufficient,
Flash is terminated
Shutter closes

The time from flash fire to flash termination is much less than the shutter
speed, typically flash duration is in the 1/10,000 - 1/20,000 sec range (or
shorter).  With the lens wide open the TTL flash meter can't quench the flash
fast enough to stop the overexposure.  There is just so much light coming in,
the meter registers the correct exposure before it can start the quench process,
more light comes in, and hence overexposure.  With the lens stopped down the
flash needs to fire for longer to achieve the same exposure so the quenching
process can begin before the correct exposure and the tail-off light completes
it.

If I could make a suggestion, try this test, get an object such as a toy car, or
a flower, something with a little depth to it.  Set your camera to the close
program and take a flash photo of the object.  Then turn off the close program
and go to aperture priority and set it for f/11.  Take another flash photo at
the same distance as the first.  I believe you will see a marked difference.
Hopefully you will be much more pleased with the second shot.  If you want to,
take a whole series of shots changing the f-stop between each from wide open to
closed right up.  This will give you a feeling for close-up work.

Sorry for the long post but some things take a bit of explaining.

All the best,

Eric

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