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Re: [OM] Ambient and Flash Ratio Tutorial

Subject: Re: [OM] Ambient and Flash Ratio Tutorial
From: Wayne Culberson <waynecul@xxxxxxxxxxxxxxx>
Date: Thu, 14 Feb 2002 09:20:28 -0400

AG Schnozz wrote:
> 
> Just to clarify something here:  When I refer to the ambient
> reading, think of this as the background.  Your flash will light
> your subject and the ambient light will take care of the
> background.  Usually the distances are such that your flash will
> have negligable affect on the background.
> 
> So, the question you ask yourself is:  "How many stops below do
> I want the background"?  With wide latitude, good handling films
> like Portra, I typically go two stops.  This gives the
> background a nice warm glow without going black.  Your subjects
> will stand out from the background without looking like cave
> dwellers.  Slide films usually need tighter ratios of 1:2-1:3.
> 
> When doing flash/ambient exposures we have only five controls:
> 
> 1. Shutter Speed
> 2. Aperture
> 3. Film Speed
> 4. Flash Power
> 5. Flash-Subject Distance
> 
> Focal-Plane shutters in our OMs limit us to nearly exlusively
> using a Shutter Speed of 1/60.  So scratch one "user-selectable"
> setting off our list.  1/60 is a fixed, known quantity.  We have
> our start point.  In lens-shutter cameras, we can start with the
> aperture if we desire.

Ag-who is able to state it so that even thick heads can almost
grasp-Schnozz
[sensitive zuikoholics may not want to read further]
        I am attending another wedding in about 2 weeks, and would like to grab
a few shots if possible. Since I won't be the official photographer at
this one (thankfully), I will be limited to, likely, non-straight-on
shots, as I don't want to aggravate the real photographer, and try to
stay out of the way, etc. So I've been trying to figure out what to take
for equipment. I know the church is huge and maybe somewhat dark, and
the background will not be close. I want to use Portra 400VC, get the
background, but get some flash on the people, too. 
        Yesterday, I took my Yashic* GSN and Achiever 632t flash into our
church buiding to do some testing. I know its a rangefinder, so
WYSInotWYG, has 45mm lens only, but hey, it's quiet! And it does sync at
all speeds up to 500. By setting the asa dial to 800 (using 400 film),
it gives one stop under exposure (it is aperture priority only), and I
can likely get f8 at 1/125, or f5.6 at 1/250. This will have to be
tested to determine at the actual site, but I have quite a bit of range
here. 
        Now the 632t flash has a GN of 32-41 ISO 100/Meters [or GN 105-135 ISO
100/feet] (head zooms), has 4 auto settings, and 2 manual ones.
Question: If I use this heretical rig for some pics, can I pick the auto
setting on the flash that matches the f stop on the camera, and just let
the flash do its thing? It occured to me yesterday, that NO, this might
not work. In thinking about this, I'm trying to understand how these
auto flashes could know distance. I think, well they obviously can't, so
maybe they are dumping a flash according to the light they read through
their sensor, and are going with a distance that fits most 'in the
normal house' kind of shot?? How do you figure out the workable
distances for the auto settings? I'd sooner not use the manual settings,
as I'd like the flash to some of the work for me, and it has a longer
recyle time (uses 4 AA's) at full dump.
        OM content: I wanted to put 2 t20's on my OM2s, but am waiting for
cords to come, and may not have time to put it together and test it. I
could put the 632t flash on the 2s, use manual mode, but I might be in
trouble with the limiting 1/60 if the church is lighter than I'm
anticipating. 
Wayne 
PS If my understanding of this looks hopeless, just ignore, and I'll get
some 800 film for the point and shoot. :-)

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