That's basically what I've been doing but I was thinking (erroneously)
in terms of ISO rather than aperture. It works the same as long as it's
within the limits imposed by the flash.
All of my training in use of flash has been to use manual mode only with
the use of a good incident flash meter. Auto mode and TTL were to be
ignored as inaccurate. Manual works very well until you get into
covering some sort of event with lots of people moving quickly in and
out of sun and shadow. It's only in the last 2 years that I decided to
try using fill flash in auto mode and I think I've used it exactly
twice. I never found any instructions on how to do it but figured it
out and tried it with good success as long as I stayed about 2 stops
down rather than 1. Being only one stop down seemed to have some
moderately high risk of blown highlights. Being 2 stops down solved the
blown highlights problem at the expense of have to do more shadow
adjustments in PhotoShop. But having to brighten shadows by only 1 stop
or so prevented the noise one gets by trying to bring up a shadow that's
nearly black.
While looking for instructions on the use of auto mode for fill flash
(pretty rare) I encountered something I'd never seen before. The
suggestion was to expose for the highlights when measuring the ambient
exposure. I've never tried it yet (too rainy the last couple of days)
but suspect that will pretty much eliminate blown highlights in the
flash exposure at 1 stop down. But I'm not sure what the background
ambient exposure will look like. Too often I see fill flash shots with
backgrounds that look unrealistically dark for a sunlit scene.
Something I haven't tried yet is to use aperture priority with auto mode
flash. I hope that will adjust the ambient exposure between sun and
clouds but I'll have to keep a close watch on the shutter speed.
I've been waiting for some sun amidst the rain and clouds. I think the
too low exposure values I was getting in my testing were due to the
flash being fooled by a too bright background. I really needed to be
outside to test daylight fill flash but haven't been able to get there.
Chuck Norcutt
On 7/15/2014 12:29 PM, Ken Norton wrote:
It's not finished or necessarily correct and shouldn't have been sent so
trying to follow a line of thought may be precarious. What flash are you
using in auto mode for fill... the T45? As I've discovered not a lot of
flashes allow for a -1 stop fill as the T-32 and T-45 do.
T45 and the 235HV.
It's very simple, really.
1. Set your ISOs the same on the camera and the flash.
2. Set your Shutter speed to your flash-sync speed.
3. With the flash turned off (to prevent the camera from getting
fooled by the presence of the flash and changing settings on you) get
your ambient exposure. Set the aperture to it.
4. Set the flash auto exposure to the setting which would be for one
stop brighter exposure than your camera's aperture setting. (If your
camera is set at F8, use the F5.6 auto setting on the flash).
That's it. However...
Due to limitations of the flash and the shutter speed of the camera,
you may need to select a different ISO to work with. Unlike the Nikon
flashes, most auto flashes have a more limited selection of auto
settings to choose from.
--
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