20D + 580EX - using internal meter

[jason_nakleh]

Hello all.. long time reader, first time poster.

 

Just picked up a 580EX for my 20D. Was using it in the house last night, with only ambient

light being a 100w incandescent bulb and the TV on in the room. Settings were M 1/60

6.3 ISO 400 with the flash on auto. The exposures were coming out fine, looked good in

the histogram. But while taking more photos I noticed the internal meter reading -2 while I

half-pressed the shutter button.

 

Does the meter not take into account the flash? If not, how do I use the meter while using

the flash? I assumed that it would take the flash into account, making it easier to meter,

but now I'm thinking otherwise.

 

Any light shed on this situation would be most appreciated.

 

Thanks!

 

Jn.

http://www.nakleh.com

[KenPapai]

Exactly -- the meter is showing your underexposure for your M settings, regardless of the flash. I find it weird too, just ignore it and bounce away (with your Speedlite).

[jason_nakleh]

Thanks Ken..

 

So you're saying I cannot use the internal meter for indoor flash photography with the 20D

and 580EX? Seems so weird.. Is it all trial and error then? Using digital this is ok, but for film

shooters this would be disastrous..

 

Is there a way to properly meter in this situation?

[jake_v]

My understanding is (and my experiences seem to support this) that the flash when used in ettl(2) mode will fire the flash for as long as is necessary, and that a sensor inside the camera will tell the flash when to stop firing (or perhaps it is the strength of the flash, anyhow... same concept) in order to properly expose your subject.

 

With the flash being completely variable, I am unsure how exactly one COULD meter the scene, as it should ALWAYS try to properly expose via flash. The exposure reading is showing you ambient lighting conditions. If the ambient light is at -2, then the background may look dark due to the light falling off from your flash, as your flash is becoming the main light for the scene.

 

So, when I teach other people how to use our cameras, I tell them that using manual mode with a flash will actually allow you to set your aperture and shutter how you wish, and that the flash will try to compensate (it can only do so much in certain situations).

 

If you were using the flash in AV mode, and you set your aperture to 6.3, your shutter speed would take a nose dive, as the camera tries to expose for AMBIENT light only... so shooting 6.3 you might end up with a 1/2 second shutter speed. The reverse is true of TV (time value) mode, if you set your shutter speed to 1/60, in that particular case, your aperture would have opened up considerably.

 

Clear as mud, eh?

[KenPapai]

Very clear -- it works exactly as Jake elucidated. Even with a wide 16-35 in M mode and bouncing your 580EX with the diffuser on you will get great results (unless the ceiling is 25 ft. high then you will have to dial in extra FEC).

[marek wondarsikay]

This also seems to be true when using the pop-up flash in M mode on the 350xt. So I would have to say the meter probably doesn't take into account the flash. Thinking about it logically, I suppose it can't do anyway, since the power of flash is variable depending on how much light is required at the moment you take the photo.

[bill_goldman]

Actually, it's very clear. EOS cameras meter ambient light and flash separately. The underexposure indication you saw in the viewfinder is the cameras's meter reading of the ambient light relative to your (manual) settings.

 

With E-TTL or E-TTL II, the camera computes the necessary flash power and duration required for the expsure mode you've selected, or in this case, to match your manual settings. This occurs just prior to the mirror rising and the exposure is made. Therefor, the camera always indicates correct exposure for flash.

[NK Guy]

<A HREF="http://photonotes.org/articles/eos-flash/index2.html#confusion">http://

photonotes.org/articles/eos-flash/index2.html#confusion</A>

[KenPapai]

As much as I love photonotes it is dismissive of the 580EX and says little about bouncing a flash with the camera in Manual mode, stuff like the OP is asking (ETTL-II, 20D, 580EX).

<p>

<i>"Sorry, but your search term'580EX' yielded no results. Please try again."</i>

<br>

reference:<br>

http://photonotes.org/cgi-bin/search.pl?input=580EX&which=a

[NK Guy]

Dismissive of the 580EX? That's an odd accusation.

 

The link posted searches my dictionary for the term 580EX. Obviously the dictionary does

not list specific products. However, the 580EX is referenced in 4 articles on the site.

[bill downey]

I found the PhotoNet article on the EOS flash system (see NK Guy above) very through and helpful.

 

Also the best advice I got for indoor use of the 580EX on my 20D was to shot at 5.6, 125, bounce flash with Sto-fen (Search 580EX on B&H site and look at the accessories for the Sto-fen). In addition set the exposure compensation on the 580EX between +1/3 and +1. Some experimentation recommend. It works!

 

Good Luck,

 

Bill