P3D Flash Cluelessness

[Michael Georgoff <Michael_Georgoff@xxxxxxxxxxxxxx>]

Got a few flash questions.  I'm clueless about flash, having mostly
stuck to the Sunny 16 for outdoor stuff.  I did shoot  some flash
pictures recently, and the results were not good, very, very dark.

I've got an older, econo-buy Vivitar 2800.  No BCPS rating, but I'm
guessing maybe 1250.  Guide number is 80.  Flash duration spec is
1/2,000 to 1/30,000th sec.  Two options: auto (using built in light
sensor) and manual.  Auto has two ranges, "blue" (range is 3 to 20 feet)
and "red" (range is 6 to 40 feet). The user guide is not very deep, not
a great help for anyone looking beyond point & shoot. My objective here
is proper exposure with depth of field.

Auto: Set  your ASA on the handy-dandy sliding scale, and use the f-stop
it tells you.  For ASA 100, and "blue" it dictates f4, for "red" it's
f2. (Never mind "red", can't imagine needing to light a subject 40 feet
away.) So, for "blue" it tells me to set aperture to f4 and shoot...
but, I don't wanna use f4, I want more depth of field!  Well, what if I
change the ASA setting?  Note that I have ASA 100 film in the trusty
Realist. If I set the flash to ASA 200, then the sliding scale dictates
f5.6, if I set it at ASA 400, then f8, and so on up to ASA 1000 for f11.
With ASA 100 in the Realist, if I set the flash to ASA 1000, and the
camera to the indicated f11, will it work (expose properly)?  I don't
think so.  I'm thinking the strobe puts out a set, consistent volume of
light, regardless of what you set it on, and a faster film speed
necessarily means you better use a smaller aperture.  And that the light
sensor is used to set timing of strobe duration, based on the amount of
time it takes for reflected light to bounce back to the unit (when light
sensed, then off).  Can anyone clue me in on this?  Sure would be nice
to able to use the auto-sensor intelligence in the unit, but I can't
figure out how to get "aperture priority" out of the auto mode scenario.

Manual: Set your ASA on the scale and the moving scale gives you f-stop
setting per distance.  For example, ASA 100.  5 feet = f16, 7 feet =
f11, 10 = f8, 15 = f5.6, 20 = f4, 30 = f2.8.  Now, imagine a near object
is 10 feet away.  The scale tells me to use f8. What to do if I want to
use f16 for DOF reasons?  (Assume ASA 100 in the Realist). If I set the
flash on ASA 400, then the scale lines up 10 feet with f16.  Will this
work?  I'm guessing it won't, as the flash puts out x volume of light
for y amount of time, and the relationship of ASA and aperture to
distance is consistent. (ASA 100 for 15 feet at f4 equals ASA 1000 at 15
feet as f16.)

Specific Question Number 1: Given my conclusions per the above, I can't
figure out to use this Vivitar 2800 unless I use it at the recommended
f-stop.. which I don't want to do, as the DOF limitations are
unacceptable.  Is my flash wimpy, or does my brain fail me?

General Question Number 1: Flash duration for this Vivitar 2800  is
rated at 1/2,000 to 
1/30,000th sec.  What conditions dictate this speed?  What if I wanted
to be Harold Edgerton in my 3D dreams, and I really wanted to get
1/30,000 out of this, how would I do it?

General Question Number 2: It is reasonable to consider "hard wiring"
two flash units together, so that the hot shoe (switch) completes two
circuits in parallel, causing a main flash and a second (fill) flash to
fire at the same time?  Yes, I know that I can buy slave sensors, but is
hard wiring an option?  I know how to solder wires, but I'm not smart
enough about flash to know if this is a knucklehead idea.

General Question Number 3: I've seen some talk about either voltage or
current levels in strobe units being high (I mean on the shoe...  of
course inside the unit, it's dangerous).  What is the implication of a
higher current in camera use?  I gotta imagine that, for example, inside
the trusty Realist, it's just mechanical situation where widest open
shutter equals closed contact points which lead to shoe).  Example: I
have a flash from a Nishika (cheap, I know) but it's got a main light
and a bounce light in the same unit,  nice idea, but I've heard they put
out a lot of current.  So what?  Can't imagine it'll eat my Realist
(worst case is arcing on internal contacts, leading to pitting, or weird
light leaks from "internal flash"). Nor can I imagine it'll kill the
strobe, as a shoe is an open point in a circuit asking for closure.
What's the deal on high current across the shoe?

I'd sure appreciate it if someone could clue me in.  Feel free to
respond off-list.

Michael Georgoff
San Jose, CA
Georgoff@xxxxxxxxxxxxxx

(PS: A ton o' thanks to all who've helped me in the past, with my
endless direct off-list emails!)


------------------------------