Need help with Canon DSLR flash settings

[BorisMD]

Hi all,

I'm going to attempt to take my kids' portrait for the annual holiday greeting card this weekend.

Here's what I want to do:

I've got a 7D, assortment of lenses, and a Speedlight 430 EX II.

I want to take the photo on Av mode, outdoors, daylight, white snow all around, with a largish aperture to blur the background. I want to use the 430EX II to provide fill light and catchlights.

So, if I put my camera on Av mode, set the aperture to around 4, let the camera do the shutter speed calculation, what settings should I choose for the flash? I was thinking that I could just use flash compensation and dial it down a few stops. Will this screw up the auto-exposure for the rest of the shot?

It seems that when I tried something like this before, the camera compensated for my using Av and the exposure got screwed up. Mind you, user error is highly likely as an explanation for this.

Thanks,

Boris

[boBQuincy]

With an aperture of f/4 in bright daylight the shutter speed is likely to be much too fast to sync with the flash (unless you use high speed sync). I am not very familiar with high speed sync but it looks promising for fill flash with large apertures in daylight.

One option is to use a ND filter to get the shutter speed down within flash sync range (1/200 or slower ?) while using a large aperture.

[mabas9395]

I agree that you'll probably need to use high speed sync under those conditions. Your camera can't sync with the flash when you're faster than 1/250th of a second. You can use the lowest ISO and a little smaller aperture to try to get your SS to 1/250th if you don't want to use high speed sync (but you'll loose the blurry background with the smaller aperture). High speed sync is handy but you do loose quite a bit of your flash power. Its the lighting bold with the H button on the back of your flash.

And as long as you use Flash Compensation and not Exposure Compensation, your exposure should be fine.

But if you don't use High Speed sync and try to use the flash, your shutter speed will be capped at 1/250th of a second and you could see some major over exposure.

[photo_chick]

Use a longer focal length to help get a shallower depth of field when you have to stop down. Also, longer focal lengths take more light to get the exposure, so it can help you with the overexposure issue too.

[bob100]

Hi all,

I'm going to attempt to take my kids' portrait for the annual holiday greeting card this weekend.

Here's what I want to do:

I've got a 7D, assortment of lenses, and a Speedlight 430 EX II.

I want to take the photo on Av mode, outdoors, daylight, white snow all around, with a largish aperture to blur the background. I want to use the 430EX II to provide fill light and catchlights.

So, if I put my camera on Av mode, set the aperture to around 4, let the camera do the shutter speed calculation, what settings should I choose for the flash? I was thinking that I could just use flash compensation and dial it down a few stops. Will this screw up the auto-exposure for the rest of the shot?

It seems that when I tried something like this before, the camera compensated for my using Av and the exposure got screwed up. Mind you, user error is highly likely as an explanation for this.

Thanks,

Boris

I agree with the others, - high speed sync, low ISO, maybe ND filter. I use manual mode when using an external flash.

[BorisMD]

Thanks all!

I used the 70-200 f/4L IS at f/4 and 70mm. I don't have a ND, and I don't have an adapter ring for my CPL for this lens, so I went with them standing in the shade, flash on high speed sync.

They actually came out pretty nice. As soon as I get home and can upload them, I will post them here so you can see my results.

Regards,

Boris

[BorisMD]

Here's what I consider the keepers (unfortunately, I forgot to change my ISO, and it was set at 400):

http://borismd.smugmug.com/Holidays/Christmas-Photo/IMG2283/1106643360_DXhsX-L.jpg

http://borismd.smugmug.com/Holidays/Christmas-Photo/IMG2282/1106643545_2ujSp-L.jpg

http://borismd.smugmug.com/Holidays/Christmas-Photo/IMG2285/1106643762_fNRQm-L.jpg

http://borismd.smugmug.com/Holidays/Christmas-Photo/IMG2290/1106645334_mSHkC-L.jpg

http://borismd.smugmug.com/Holidays/Christmas-Photo/IMG2291/1106650053_uKadg-L.jpg

Not yet sure which one we'll go with, but it will certainly be one with both kids (and not the furry one!).

Regards,

Boris

[SplashMo]

I like the first one.