I'm a wedding photographer working with 40/50D with 580EX2 and 430EX2 on top of both cameras hot-shoes for fill-in purpose. I shot both cameras in "Av"mode with auto ISO, both flash set to TTL and -1-1/2 stop (under) to fill-in the subject (mostly people) without caused a hard flash look in order to maintain the sharpness of the subject(people), as well the mood.

but I found both flash come out it is as bright as normal, even brighter than normal sometimes, its not regulate.

Anyone can point out could it be my setting wrong, if how can I set the flash as fill-in mode.

Thank you

Paul

That should not have happened. If you dialed in a lower flash output on the flashgun, you should have gotten less flash output for any camera setting. The only thing I can think of is that the flash was not taking into consideration the auto ISO.

Really nice stuff on your website. Inspired me.

i don't think this is your problem, but i've found it necessary to check that the flash is set to high speed synch when using fill flash - seems like i sometimes bump the button or something, and flash in normal synch forces exposure at maximum synch speed

Do you use Av mode for indoor shoots? Like inside the church? If so, you'll do better if you set the body to manual and flash to E-TTL.

The E-TTL system is not perfect, and often overexposes the subject in a dark room. The -1.5 stops is a good setting for outdoor fill -- where the background has the same general lighting as the foreground -- but it may still be too much for an indoor shoot.

I shot an awards ceremony Thursday in which the subjects were on stage with a black curtain as the backdrop. Even at -2 EV the flash was a little bright.

I will second the recommendation to shoot in Manual Mode on the camera body when shooting indoors. Aperture Priority allows too slow a shutter speed under many conditions. I end up shooting ISO 800, f/4, and set the shutter speed to allow a little of the background to show up. The flash provides most of the light on the subject (and of course is filtered to match the ambient light color.)

For TTL In dim ambient conditions, the camera settings (f/ stop, shutter, and ISO) only affect the background brightness and not the subject brightness but in bright conditions the ambiant light will be added by both the camera AND flash metering system meaning overexposure - this is why Nikon has TTL-BL (balanced flash) for fill flash use.

So many auto functions going at once (auto ISO, Av and TTL flash) makes it difficult to diagnose the issue, try shooting manually with TTL and see what happens.

I second the comments about shooting manual. However, there are times when shooting Av is preferable, particularly when ambient light is the determining factor of the look you're after.

I think your problem is possibly with your ISO. I've found that using fill flash with ISO above 400 causes exactly what you're writing about. I've even had it happen with ISO 400 (when I was outside and 400 was too sensitive). What ISO were you using?

i'd check the high speed synch frequently as i find it often get's dropped for reasons that i can only speculate on

i've also had no problem using fill flash in AV mode

It sounds like you shoot indoors in Av, because I find E-TTL with body in Manual to be near perfect indoors, low light, bright light it don't matter. Av does not beling indoors with few exceptions. Indoors most often demand camera in manual, flash utilizing E-TTL.

..and that is why one should not use Av with indoor flashing, unless for those rare occassions when fill is required to work with the desired ambient light level.

Otherwise, manual camera, E-TTL flash means the camera exposes for the background, the flash for the subject, and this is ideal for weddings indoors. Doing this provides excellent results, and results that are repeatable and predictable too.

Nope, reread my answer. I shoot manual mode for this type of assignment.

If you are getting "perfect" E-TTL indoors, then you are the first Canon shooter I have heard of who is. Congrats on that.

One thing that may be helping me is that I do something most shooters don't do: I manually pick and choose the appropriate focus point, don't recompose, and I set the flash to meter with evaluative mode. I have found that doing this with the body in manual, and flash set to utilized E-TTL results in excellent exposures.