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More on flash fill-in (was Re: [OM] TTL auto shutter speed question...)

Subject: More on flash fill-in (was Re: [OM] TTL auto shutter speed question...)
From: "Enrique Cabrera" <qcabrera@xxxxxxxxxx>
Date: Thu, 7 Jun 2001 15:29:36 +0200
Jim:

Thank you for throwing some (flash) light into the somehow obscure 
world of TTL beginners. However, I have a few more questions on the 
matter for the list (sorry Zuiks, I'm pretty sure that the archives 
are full of this, but Jim was SOOO educational <g>).

- I always have thought that the main fill-in flash use was to 
provide some light for a subject against a very bright background. If 
you do that in Auto, the averaged meter reading may not ask for 
flash... Should I assume TTL is of no use there? (subject will come 
out dark, background bright)

- Let's suppose that I am aware of the previous fact, and hence I 
spot meter the subject and not the background. How do I use the spot 
meter reading in my OM 2s and the manual flash setting to get the 
correct ammount of fill?

- You suggest to use TTL flash in Auto mode, with ISO 64 film, and 
f16 aperture. Shutter speed will increase from, let's say, 1/15 to 
the desired 1/60, and you may get great depth of field, but objects 
further away from the flash range will be underexposed... right? 
Wouldn't it be better to shoot at f8 or f11?

Please be gentle to the Spaniard... I promise to do my homework and 
present it to the list, so you can see that your advice is well used! 
:)

Cheers


Once Upon a 7 Jun 01, Jim L'Hommedieu wrote me about [OM] TTL auto shutter 
speed questio something like:

> But if you put in Kodachrome 64 and use a polarizer, and you're still at f
> 16, in full daylight, pointed at an average scene, suddenly the "correct"
> exposure without flash is around 1/15.  This is where it gets interesting.
> If your flash is in a TTL shoe but it's switched OFF, you get 1/15 at f16
> without flash.  But if the flash is ON (and set with the TTL panel facing
> correctly, duh) the camera will open the first curtian, ask for the flash,
> sense that it has correct exposure (mostly from the flash exposure) and
> close the second curtian.  Total shutter duration: Sync speed, 1/60th.
> Although the viewfinder was telling you the shutter speed _predicted_ was
> 1/15th, the flash shut the curtian at the sync speed of 1/60.  This is
> correct operation.


Enrique Cabrera Jr.
Industrial Eng., MSc
Asst. Professor
Fluid Mechanics Group - Institute for Water Technology 
Politechnic University of Valencia (Spain)
http://www.gmf.upv.es
Tel: +34 96 3877611
Fax: +34 96 3877619


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