Paul Warren wrote:
> I'd now like to learn some more about fill-flash. I understand the basic
> concept, but I'm confused about equipment. My ZX-M came with the
> AF201SA flash, but my understanding is that it's not very appropriate
> for fill flash. If I'm wrong, let me know! Anyway, I'm mostly confused
> about the terminology surrounding flashes (manual, auto, TTL, non-
> TTL) and what will and won't work with the ZX-M. Any enlightenment/
> suggestions on technique/equipment?
Hi Paul,
Welcome to the list! Maybe I can help you out. Hopefully one of the other
list members can help you out if I lead you astray. Pardon the long
answer....
MANUAL: You figure out the proper lens aperture and subject distance from
the flash unit's guide number. For instance, I believe your AF201SA has a
guide number of 66 (in feet). Provided you are using ASA 100 film, the
correct lens aperture multiplied by the correct distance-to-subject will be
equal to the guide number. For example, you might use ASA 100 film, a lens
set at f/4, and a distance to your subject of about 16 feet. This will give
you a *fully illuminated* subject. (This is different from fill flash --
more on that below.) If you use film faster than 100 speed, just multiply
the guide number for your flash unit by the square root of the speed ratio.
Thus, for 400-speed film, the guide number would be 66 times the square root
of (400/100), or 132. You could thus shoot subjects about 32 feet away at
f/4, or about 16 feet away at f/8, for example.
Just to complicate things further, some flash units will allow you to
discharge the flash at less than full power. Many of the Sunpak units, for
instance, allow you to discharge at full power, 1/2, 1/4, or 1/16.
For fill flash, you generally don't want all of the light illuminating your
subject to come from the flash. Your subject may be partially illuminated
by the sun or other ambient light, and you just need a little extra to
partially fill in some of the shadows. If you're shooting people, keep the
sunlight out of their faces to avoid squinting, etc. From your distance to
subject, calculate the proper aperture for full flash illumination, then
stop down the aperture a bit (perhaps a stop or two further, to allow for
less light on the subject). Using your camera's meter, calculate the
correct shutter speed to properly expose the background of your scene at the
aperture you just set your lens to. Hopefully the correct shutter speed
will be slower than the X-sync speed for your camera (1/100 sec for the
ZX-M, if I remember correctly). This is where a variable-power flash unit
sometimes comes in handy.
AUTO: A little sensor on the front of the flash unit measures the flash
intensity reflected off the subject. When enough light has been detected,
the flash unit quenches (or shuts off) the flash. Thus, the duration of the
actual flash will be longer for darker scenes and shorter for lighter
scenes. You can generally do fill flash with these types of units by either
setting the film speed dial on the flash unit to a faster film speed than
you have loaded, or by stopping down your lens a bit further than the
"correct" aperture displayed on the indicator scale on the flash unit.
TTL: "Through-the-lens" metering. A little sensor inside of your camera
measures the flash intensity at the film plane. Your camera body would then
tell the flash unit when to quench the flash. This requires a dedicated
flash unit, specific for your camera, and a TTL-capable body. If I remember
correctly, the ZX-M is not capable of TTL metering. Generally, non-TTL
units are AUTO.
A NOTE ON EQUIPMENT: You may wish to pick up a more versatile flash unit at
some point. A useful feature to have is a bounce head -- one that can be
angled from horizontal to vertical. Another useful feature is a swivel head
-- one that can be rotated from a straight-ahead position to an
off-to-the-side position. This way, you can bounce the harsh flash off of a
ceiling or wall to get a more diffused and natural light.
Hope this helps. Good luck!
Bill Peifer
Rochester, NY
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