Bit confused about determining lighting.

[samueli]

Most of the lighting tutorials I read/watch talk about dialing the flash in to a particular aperture. I have canon speedlights that I use in manual mode, and as far as I know I can only adjust power and zoom. I can manage as a lighting newbie to I guess chimp my way for now, but it would be nice to get onboard with proper calculation and learn the proper technique. How can I do this with speedlights? Any thoughts or suggestions?

[krb]

As you said, flash doesn't have an aperture. You just set the power level and perhaps a zoom. The aperture is only on the camera and is used to help get the exposure correct. people say to use the aperture to control exposure because you are normally limited to 1/250 or less on shutter speed.

There are 3 ways of getting the flash level and camera exposure settings correct:

- Take test shots and chimp the histogram until you get it right.
- Use a flash meter from a company like Sekonic
- Have so much experience that you can just look at the scene and know the right settings.

[samueli]

So why does the vivitar flash have fstop settings? There is plenty of reference to setting flashes that way.

[krb]

Oh, that. Those are not used for manual control, so far as I know. In the days before TTL metering flashes had "sorta automatic" modes where you would dial in some variables and it would set the flash level based on what you entered.

[bobbyz]

So why does the vivitar flash have fstop settings? There is plenty of reference to setting flashes that way.

I think those are when using the flash in auto mode.

[Wilt]

I think those are when using the flash in auto mode.


^ When the flash uses its own photosensor 'Auto' mode), it is not seeing the light coming thru the lens ('ETTL' mode) of the camera. So you have to tell it what f/stop is set on the lens, so it can regulate its light output to suit the f/stop in use.

[Wilt]

As you said, flash doesn't have an aperture. You just set the power level and perhaps a zoom. The aperture is only on the camera and is used to help get the exposure correct. people say to use the aperture to control exposure because you are normally limited to 1/250 or less on shutter speed.

There are 3 ways of getting the flash level and camera exposure settings correct:

- Take test shots and chimp the histogram until you get it right.
- Use a flash meter from a company like Sekonic
- Have so much experience that you can just look at the scene and know the right settings.


4. know the Guide Number of the flash, and use that to compute the f/stop to use for the flash-to-subject distance of the shot.

[Titus213]

In the method Wilt has presented you need to know the Guide Number of the flash at the specified zoom setting - it changes.

http://photonotes.org/cgi-bin/flash-lookup.pl?flash1=canon430ex&flash2=*&flash3=*

ISO also plays into the computation.

[Benji]

Purchase a light meter.

Benji