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design22

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how to achieve fill flash with the 20D? using the built-in flash, I mean. The manual doesn't have an entry for it, nor does it touch on this. I'm quite happy with the flash and the way it works. Just want to know how to work it for "fill" purposes, say on a cloudy day, photographing someone under a tree, where shadows darken the face. A little bit of fill flash would help, but I only know how to use the flash full force.

would flash compensation be the answer? and if so, how much to give or take? trial and error?

many thanks
d/22
 
http://photonotes.org/articles/eos-flash/
design22 said:
how to achieve fill flash with the 20D? using the built-in flash, I
mean. The manual doesn't have an entry for it, nor does it touch on
this. I'm quite happy with the flash and the way it works. Just
want to know how to work it for "fill" purposes, say on a cloudy
day, photographing someone under a tree, where shadows darken the
face. A little bit of fill flash would help, but I only know how to
use the flash full force.

would flash compensation be the answer? and if so, how much to give
or take? trial and error?

many thanks
d/22
Click to expand...
 
The Av and Tv modes will both use the flash for fill when the built-in flash is up or an external flash is mounted in the shoe. It is in the manual, just look in the section about the flash using Av or Tv modes.

Brian A.
 
I'll check, thanks. But on principle I prefer to use manual settings. Any way to do the same manually?

thanks!
 
design22 said:
I'll check, thanks. But on principle I prefer to use manual
settings. Any way to do the same manually?
Click to expand...
Yes, you could expose for ambient manually and use negative FEC, probably one stop or so, for the flash. The amount of flash needed will vary greatly depending on the lighting conditions.

If you are doing this outdoors and the shutter speed gets to high for the flash sync speed, then you will have to use FP (high speed) sync for the flash.

Brian A.
 
okay, I checked the manual. For Tv or Av I see nothing about flash use. Am I missing something?

And while on the topic, why is Tv or Av better than using manual settings indoors?

thanks!
 
Ooops! I reread the post and realize I misunderstood the tip about using manual. To rephrase the question, why is Av or Tv better than manual for outdoor shots? I always have to use compensation anyway!

thanks!
 
AV or TV expose for the ambient light, and then light the foregroud giving it the same exposure as the ambient light. For example, in a bowling alley the background was all lit up, but my subjects were in the dimly lit area where the bowling balls were. I used AV, and the camera exposed for the brightly lit areas in the background and the flash then lit my subjects in the foreground. Easy. Even if I didn't like the flash amount I could use FEC and dial it down and still achive ease of use. The same priciple applies to outdoors use. Beware, if the backgound is dark, then AV or TV will again expose for the ambient light, and that will be very dark in that case. But you said you wanted fill flash, and that occurs when you want to brighten up the foreground-tailor made for AV/Tv.

-Bruce
 
thanks for the clear explanation. But how different is this from getting a manual reading by focusing on the subject, then setting the exposure accordingly and using flash for fill?
 
With a flash, manual isn't really manual, it is an adjustable semi-automatic mode – you set the shutter speed and aperture and the camera tries it's best to output enough flash to cover the exposure. Providing the shutter speed is below the max. sync speed (1/200 or 1/250s) and the flash has enough power for that aperture, everything should be fine.

The only way to get truly manual flash is with an external flash set to manual – you can then use the guide number and the distance to the subject to calculate the correct aperture (the shutter speed doesn't matter providing it is below the sync speed because the flash burst is just a few milliseconds). You can't do a manual exposure for flash with ETTL – it is a contradiction.

There is no full time flash metering, the metering reading you see in the viewfinder is always that of the ambient light. Flash 'metering' takes place after you press the shutter release, a split second before the shutter opens, when the 'preflash' fires. From the preflash burst, the camera/flash calculates how much power it will need for the flash burst proper. (The preflash will also fire when you press the FEL button.)

With the Canon flash system, both Av and Tv modes are fill modes: In Av, for example you set the aperture and the camera sets the correct shutter speed for the ambient light, not the flash. The camera fires the flash at about –2/3 stop below the ambient exposure setting, unless you use FEC.

Manual mode, with an EOS flash in ETTL mode, is often seen as better for situations where you want the flash to be the dominant light source.

I hope this helps,
Brian A.
 
In my bowling example what exposure should I have made for my foreground subject? What I wanted was to equal the background exposure. Ok you'll now say that you can do that by figuring out what the exposure is the for the background. Yes you could. Choose.

Consider a subject with a rapidly dwindling sunset in the background. What exposure for your subject? Until the ambient light is too low for a proper exposure I think you'll find that AV with fill flash is easier.

Have fun experimenting.

-Bruce
 
If the background is bright enough, any automatic mode (P, Av, Tv) is OK. Just make sure the shutter speed is not above 1/250.

For subjects under noon day sun, dial back Flash EC by 2/3 to 1.5 stops to prevent the wash-out look. It still fills in the hash shadows around the eyes, under the nose and chin.
Have fun.

--
Peter Kwok
http://www.pbase.com/peterkwok
 
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