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[OM] Re: Q for Dr. Flash et al

Subject: [OM] Re: Q for Dr. Flash et al
From: AG Schnozz <agschnozz@xxxxxxxxx>
Date: Wed, 18 Apr 2007 13:14:37 -0700 (PDT)
I'm going to second Dr Flash's recommendations with a couple slight
changes and observations:


1. Digital is NOT tolerant of over-exposure.  There are some of us
that grew up underrating the professional print films. We did this to
get a bit better saturation and contrast in the negatives. However,
print films have what is known as a "shoulder". Digital, as a general
rule, does not.  It is more important today to get the exposure as
close to dead-on as possible.  The days of leaning into the shoulder
are over.

2. Digital is highly picky when it comes to white-balance. Film
engineers spent decades perfecting the way a film would respond to
certain types of light.  The color response curves were anything but
linear. A daylight balanced pro print film would warm under
incandescent light, but a digital image will yellow.  When shooting
with flash, the very best thing to do is select "daylight" (5200) for
your WB. Auto-WB will usually turn your pictures all sorts of
colors--mostly blue indoors.

3. Manual-exposure mode.  It's funny that through all these years of
advances in automation that the old way is usually the best way.  I'd
kill for an "OTF" E-x that operates just like the OMs did (with the
addition of fill ratios).  Lock in the aperture as per the
recommendation on the flash.  Then adjust the shutter speed to
accomodate either the camera's fastest sync-speed or for an exposure
of the ambient light about two stops down.

4a. Manual-flash mode.  This is optional.  I know Dr Flash is a firm
believer in locking in the flash power.  I'm not quite so adament. 
But when you are working beyond 15 feet (5 meters), manual-flash is
always going to give you the better exposure.  Or...

4b. Auto-flash mode.  This is my preferred setting most of the time. 
My flashes of choice are the Vivitar 285HVs which have an outstanding
auto-exposure sensor built-in. They also have three auto-levels and
four manual-levels to choose from.  Mine lives in Yellow.  Again,
program the camera with the recommended aperture.  Why I like
auto-flash is that my background (ambient) light-level always remains
constant and the flash takes care of my subject.

5. Test to adjust your exposure setting.  Just like the film days
(see above), you may need to over/under-expose the flash to get the
results you want.  As a general rule, I choose to overexpose my 285HV
about 1/2 stop, but that's to match up for my system and my way of
working.

6. Light modifiers can bite you.  The biggest problem with some
light-modifiers is that they "splash light" into the flash's exposure
sensor.  Another factor is they change the output-levels so the
fall-off ratio is different than the normal straight-ahead light. 
The way an auto flash works is the sensor measures the reflected
light from the flash and will quench the flash at the appropriate
moment to prevent over-exposure.  However, no quench-circuit is
"instant" and the factory has calibrated it to a given lag-time. 
However, the amount of light being emitted and reflected by the
subject in a "straight-ahead" exposure is different than if the light
is bounced or modified. Depending on the flash system, you can end up
with as much as a 1-stop variance.

7. Practice, practice, practice.  I borrow one of my girls big teddy
bears for flash practice and calibration. No two cameras or flashes
will be the same.  I've got at least 20 hours into test and
calibration of just my on-camera flash systems.

AG

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