BetterPhoto Q&A
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EV for flash

Thanks
John

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August 30, 2007

Ev is EV no matter how you look at it.

+1 be it flash or Aperture or shutter are the same exposure. Period.
Obviously if the subject is out of the effective EV of your flash, you no longer can count it.

This is NOT to say the same (effect) is attained. (i.e) Depth of field and Freeze or blur.

Raising flash power is only one way of course to adjust exposure.

So; +1 flash with +1 on camera = +2

There are of course limits in what you can and can not do. Ex: +1 w/ flash and +2 with camera when shooting aperture priority might freeze your subject and also may cause a blurred background if you drop too low in shutter speed.

So; yes...Using gels on the flash with a diffusion dome will require some + compensation in (manual) and aperture modes. In (program) mode it will make no difference as the camera has taken control of aperture, shutter,flash quench and power output in a attempt to make a balanced exposure. The "effective" EV of the flash is of course reduced.

I rarely use Program anything with a camera..You see the info on speed and aperture, but you can do nothing about it. Sure you can dial in a + or -...but what did the camera do?..Raise or lower speed, aperture, or both? That's why it's called program..It has been "programmed" with specific speed/aperture defaults to give what it (thinks) will be a balanced exposure. The D-70's manual has a graph on HOW it selects speed/aperture.

The best way to actually measure the amount of standard compensation would be to use a flash meter in manual mode..with and without the gel and diffuser.

Hope this helps a little.

Pete

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August 30, 2007

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August 31, 2007