Re: [OM] Dr. Flash learns a thing or two... on auto flash

[Chuck Norcutt]

Correct.  In flash parlance "auto" means exposure control by the flash 
using its own sensor, not TTL which (as you have guessed) is called TTL.
What was said is you can do fill flash with an auto flash unit by first 
setting the ambient light exposure on the camera.  Let's say it's ISO 
100 at f/11.  You then transfer the same ISO as used on the camera to 
the flash unit and set the aperture on the flash at a one stop wider 
aperture than is set on the camera.  In this case you'd set the flash at 
ISO 100 and f/8.  Because the flash thinks the camera is set at f/8 
rather than the actual f/11 it thinks the camera is more sensitive to 
light than it actually is and delivers only half of the light that would 
be otherwise be required.  Other values may be used but a 1 stop 
differential between ambient and flash is typical for fill flash in full 
sun.
The other key point is that not all auto flash units have suitable 
settings to be used for 1 stop under fill flash.  The T32 and T45 have 
three auto ranges which are one stop apart so you have a good chance of 
finding a suitable setting.  Most of the other flash units I have here 
(except for the potato masher Sunpak 522) all have 2 or 3 auto range 
settings but they are all 2 stops apart.  If you use 2 stops you may 
have to do some more shadow fill in PhotoShop.  But you're also less 
likely to blow some highlights that get hit by both ambient and fill light.
Chuck Norcutt


On 7/15/2014 3:58 PM, Moose wrote:
> On 7/15/2014 7:07 AM, Ken Norton wrote:
> > Not sure I'm following your line of thought,
> Didn't read it all. I'll wait for the finished version. :-)
>
> > but I will say that I use
> > auto-flash as outdoor fill-flash as a matter of course.
> It's been a loooong time. I recall being regularly impressed at the
> ability of OM-2n with T32 on TTL Auto to balance fill flash.
>
> But I'm guessing this may be about the flash based sensor, not TTL??
>
> Flash? What Flash Moose
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