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Re: [OM] what happend to my flash shots?!

Subject: Re: [OM] what happend to my flash shots?!
From: Acer/Siddiq <waltherppk@xxxxxxxxxxxxx>
Date: Thu, 24 Jan 2002 21:57:45 -0800
1/24/02 4:39:00 PM, "John A. Lind" <jlind@xxxxxxxxxxxx> wrote:

>Acer,
>The clues:
>(1)  One T-32 with a diffuser effectively making it about the same as a 
>T-20 without one.

right, effective GN was ~23

>(2)  Fuji NPS (not a bad film choice; the film speed is the key).

haha! 

>(3)  Lens aperture set to f/8.

Well, i looked at the flash calc panel before i went out to get film, and this 
is what i figured:

1) diffuser would lose me no more than 2/3 stop (measured light w/ gossen light 
meter--regular, not flash--
with and w/o diffuser pointing to the sky). round it to 1stop even, giving a 
slight overexposure for safety 
margin

2) so instead of 160, figure effective filmspeed for GN calcs as 80

3) with T32 calc panel set to ISO80, 12ft range gives me f/8 normal auto, 
decent DOF

with those three points, i figured i'd be OK....

but i guess not!



>See my "wedding" tutorial about the need for flash power (scroll down to 
>the tables of film speeds, apertures, distances and flash GN ratings [given 
>for ISO 100]):
>   http://johnlind.tripod.com/wedding/rightstuff.html#equipment
>   <http://johnlind.tripod.com/wedding/planning.html#Exposure and 
>Lighting>http://johnlind.tripod.com/wedding/planning.html#Exposure and Lighting

ah yes, i'd read that when you first wrote it. i suppose a refresher is in 
order.

>I suspect you simply did not have enough flash power.  I must watch 
>carefully when using Kodachrome 64 indoors that I keep aperture to f/4 or 
>f/5.6 lest I run out of flash power with a single T-32.  If this was a 
>"reception" held in a reception hall or banquet room, distances are 
>deceptively farther than inside someone's living room!  This is one of the 
>reasons the pros use very, very powerful flash heads for "event" 
>shooting.  It allows stopping the aperture down to f/8 and still being able 
>to throw enough diffused light over 20 feet to properly expose ISO 100 or 
>ISO 160 film.

and then there's no stray "bounce off the side walls or ceiling" light to 
augument the subject! further 
lowering the GN (which i know manufacturers report for indoors to get a few 
more feet range)

>A T-32 with the 21mm WA diffuser is effectively a T-20.  At f/8 you only 
>have enough flash power for a maximum distance of about 8-10 feet.  You 
>need to run something more powerful than a single T-32.  This is something 
>I suspected and confirmed during my first wedding shoot as an "apprentice" 
>with a local pro.  You need a GN of about 150-160 [ISO 100 in feet], 
>*after* taking into account any diffusion or bounce device you use.  It's 
>the reason I used a pair of T-32's on a bracket without diffusers!

I guess I might have to do direct T32, no diffuser, or step up to NPH. I like 
the no diffuser part better, so i 
can shoot closer scenes w/o stopping down too much.

>If you decide to shoot the wedding for them, start at the beginning:
>   http://johnlind.tripod.com/wedding/

oh no! I'm just doing this on the side cuz I can and want to!

>-- John
>[who doesn't claim to be a great wedding photographer; just one who 
>understands many of the technical issues associated with it]

...and many other technical (and philosophical too <gg>) issues :) great to 
have made your acquaintance!

/A/S
--
dum spiro, spero
http://users2.ev1.net/~wesiddiquis/siddiq/



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