We've talked about lenses, features, and cameras. Now it's time to
look at your portable light source, electronic flash.
Built-in Flash Considered
Almost everyone starts out with a zoom lens, whether 28-80 or
28-200. Keep in mind that your typical zoom lens these days is f/3.5 at
the short end (2/3 stop slower than f/2.8) and f/5.6 at the long
end.
The built in flash has a guide number (GN) of approximately 40 (in feet)
with ISO 100 film. (The guide number divided by your f-stop tells you
the maximum flash range.) With 100 speed film and your zoom set at the
long end, f/5.6 means you should be no more than 7' from your subject
for proper exposure.
Thanks to the exposure latitude of modern color print films, you
can get acceptable results up to about 10' and recognizable ones at up
to maybe 14'. That's it.
The guide number increases with film speed. For each doubling
of film speed, the GN increases by 40%, so at ISO 400, the internal
flash has a GN of 80 and a reach of 14' with your lens at f/5.6.
I hope this helps you understand why so many pictures of school
stage shows shot with flash are underexposed - unless you're using 800
or 1600 speed film, the standard flash with the typical zoom just doesn't
have the reach you need. This is one good reason to consider adding a
more powerful flash (ISO 100 GN of 80-120) to your setup.
Zoom Lenses Considered
Besides film and a more powerful flash, the third way to increase
flash distance is a faster lens. Although today's cameras commonly come
with a 28-80/3.5-5.6 zoom, there are alternatives. Some are
horrendously expensive, such as a 28-105 with a fixed f/2.8 aperture.
They're also quite heavy.
If you'll be doing a lot of flash photography in larger areas, think
about a 28-105/2.8-4 (or so) zoom such as Sigma, Vivitar, and Phoenix
offer. These are up to a full stop faster at the long end than the most
common 28-80 and 28-200 zooms. That one stop difference increases your
flash range by 40%. Coupled with fast film and a powerful flash, this
can be quite a combination. (It's too bad neither Tamron nor any of the
camera makers [except for Sigma] offer such a lens.)
What About Zoom Flash?
Odds are you'll hear someone extol the virtues of a zooming flash
head, especially one that automatically zooms as you zoom your lens.
That sad truth is that while a zooming flash head increases the guide
number slightly, it's rarely enough to make much difference. In my
opinion you're better off without the zooming flash head; invest in a
more powerful flash, and you can still save money.
For instance, my favorite flash for the past 20 years was the
Sunpak 422/433/444 series. The
433AF has a GN of 120, giving it three times the reach
of the flash built into most of today's cameras.
Sunpak's more expensive
PZ4000AF zooms from 28mm to 80mm and varies its GN from
80 to 132. At the long end, it provides 10% more reach than the 433AF.
Yet the 4000 costs one-third more, is considerably bulkier, and is more
complex. If you really need some reach, look at the PZ5000AF, which has
a GN from 99 to 180 and provides fully 50% more range than the far less
costly 433AF. Of course, it costs about twice as much as the 433AF.
Other Factors
Flash is one area where camera manufacturers distinguish themselves.
If you want high speed flash sync, you're pretty much limited to what
Nikon, Minolta, etc. have to offer. The same goes for off camera flash
sync. These flashes are not inexpensive, but they may offer features
Sunpak, Vivitar, Metz, and other simply cannot provide.
By now my bias should be clear. I think a good flash is one of the
most important things you can own if you do a lot of indoor
photography. I'm particularly fond of the Sunpak line, which I've been
using without any problems since 1977/78.
Next: Putting Your System Together
