580EX/EOS3 Confusion

[hugebob]

Hi All,

<P>

I'm about to delve into portraiture and I'm following the guidelines of <B><A

href="http://strobist.blogspot.com/">The Strobist</a></b>. Working in manual is

the mode of choice and that's where my question comes in. If both the camera

and flash are set to manual, does the flash take the manual exposure settings

from the camera and apply manual flash settings to that? Basically, what I want

the flash to do is take my manual camera settings. Then, apply my dialed-back

power output (1/2, 1/4, 1/8, etc.) settings. Is this what happens?

[digitmstr]

You MUST adjust the power output on the flash body. There is no way to adjust the power output of the flash from the camera (exc. for FEC).

 

So, in your case you put BOTH camera and flash in manual, take a reading with a FLASH meter then, adjust the flash power accordingly using the dial on the flash itself.

[cliff_henry]

"...does the flash take the manual exposure settings from the camera and apply manual flash settings to that?"

 

No! If flash is in manual mode then its output is controlled by its own setting.

 

To uses flash in manual mode you will need a flash meter or do the histogram dance.

 

I like to set camera to manual but set flash to ETTL and adjust lighting using flash compensation.

 

This may help:

 

http://photonotes.org/articles/eos-flash/

[hugebob]

Oh, Ok! So, in ETTL mode, the flash is in auto and is using the settings from the camera to set exposure/output power? If so, I can accomplish what I originally wanted by using exposure compensation on the flash which is the same as dialing up/down power output. Do I have this right?

[PuppyDigs]

The M mode on the camera is for ambient light exposure. M mode on the flash is only for

flash output. By using the two separate systems in manual you have ultimate control of both

light sources. For example, you can set amibent according to the meter and use flash as fill,

or underexpose ambient and use flash as main light. Sounds like you need to study NY Guy's

EOS Flash Bible.

[cliff_henry]

"...the flash is in auto and is using the settings from the camera to set exposure/output power? If so, I can accomplish what I originally wanted by using exposure compensation on the flash which is the same as dialing up/down power output."

 

Actually, the flash has its own exposure meter and adjust flash output, i.e., how long it will stay on and not its power output, which is always the same. The longer the flash stays on, the more light that reaches the subject. The flash and camera do communicate but the flash is not adjusting to the camera's settings, but rather its meter is reading the reflection from the main subject to determine flashes output (duration).

 

Adjusting the flash output using flash compensation should give you the results you want.

 

When setting your camera in manual mode, remember that shutter speed will determine the exposure of your background and f-stop setting will determine DOF and exposure on main subject.

 

There may help:

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00GFuJ&tag=

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00GOXj

[h.l.]

To do what you want, keep the flash in auto (ETTL) and use the camera's Flash Exposure Compensation (FEC) to adjust the flash power. The camera can be in Av, Tv, or M depending on what you want to do with the ambiant light.

[jim_larson1]

<i>Actually, the flash has its own exposure meter and adjust flash output</i>

<p>

Ummmm. . .no <p>Canon flash units have no metering capability whatsoever. When set in ETTL mode, the flash unit will emit a preflash. The output of the preflash is judged by the exposure sensors <b>in the body</b>, and the body then sets the flash power. You can adjust flash output with FEC. Works the same with multiflash setups.<p>

In a single flash setup. . .if you set the flash to "manual", it is in manual. You set the power based upon your good judgement. Works a bit different in multiflash (if you set a slave to manual, only the slave is in manual).

[cliff_henry]

Thanks Jim, you are correct.

 

I try very hard to not put out bad or misleading info on PN. I know what Jim said is correct but I guess I just had my mind some where else and should have slowed down long enough to check my facts.

 

Sorry if I confused the issue Robert.