White Balance when bouncing the flash

[toddb]

My setup:
10D, 550EX with an Sto-Fen Omni-Bounce (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=89908&is=REG)
Lens is a 28-135mm IS with a B+W UV filter
I have 9 foot ceilings (white) in my apartment, I point the 550 up and slightly forward.

Problem:
I normally shoot raw because I never have been good at correcting for WB. I've notice all my bounced shots have a red tint. The camera AWB sets for about 5850 and my correction is usually 5200.

Case Study:
Here are two shots with the same camera setting. [1/60, F/8, iso 400, 28mm focal length] The only difference is that the 550 with the Omni-Bounce is pointed straight on and the other bounced. I've auto contrast (as to keep the colors the same) and resized in PS. I shot both in High Jpeg mode so I don't know what the WB was shot for each (is there a way to find out? I usually can see it in the Raw Converter in PS, does the Jpeg retain this info?).

Direct Flash with Omni-Bounce
http://www.toddburke.net/forumpost/direct.jpg

Bounced Flash with Omi-Bounce
http://www.toddburke.net/forumpost/bounce.jpg

So I think my solution is to follow the instruction in the 10D manual on page 53 to set 5200K in the color temp parameter in the menu and use the "K" in my WB selection.

I've tried using that card in the back of Scott Kelby's "The PhotoShop CS book for digital photographers", but it's got a glossy coating on it so I'm having a hard time with the glare. First of all, that's not so good anyway because most of my shots are just spare of the minute shots of my daughter when she is doing something cute. Also, I'd like to get good enough that if I wanted to shoot JPEG, I can without too much manipulation in post processing. Even though I have a "fix" for my situation (as long as the lighting stays consistent), I'd like to understand why the bounce of the flash warms the WB up like it does. Maybe if I understood this better I'd be better able to anticipate WB in my shots without so much post processing.

Thanks for any insight.


Here is another shot side by side of AWB and my correction with this setup:
http://www.toddburke.net/forumpost/orginal.jpg
http://www.toddburke.net/forumpost/corrected.jpg

I think my first problem is that I should never have color corrected my monitor. LOL

[slejhamer]

I'd like to understand why the bounce of the flash warms the WB up like it does. Maybe if I understood this better I'd be better able to anticipate WB in my shots without so much post processing.


It's possible that the Omni Bounce is the cause of the color cast, or at least part of it. You should compare bounced flash with and without the Omni.

However, the primarily culprit is more complex than that. First, if you are using Auto WB, then the camera will automatically choose Flash as the WB when it senses the flash. However, it does not know that you are bouncing the flash. So...

If you shoot with the flash straight on, the flash is the primary source of illumination. (I'm assuming you are not using fill flash, as it certainly doesn't look that way from the images.) Flash WB is then appropriate though many will argue that Daylight WB can give more pleasant results when using flash.

When you bounce the flash, with or without the Omni, ambient light plays a much bigger part. Your bounced light from the flash has to travel much further than before (up to the ceiling and back down), and it becomes very diffuse and - here's the kicker - mixed with the ambient light. But remember, the camera has picked Flash WB. If you have indoor tungsten lights turned on, you're going to get a color cast.

You have three choices for dealing with this:

1. Shoot a frame with a white or gray card in the same light, then use this frame as the reference white balance when you convert from RAW

2. Use some sort of light diffusing add-on (expodisc, coffee filter, etc.) to shoot a gray frame and set custom white balance in the camera (see the recent expodisc thread on this forum)

3. Adjust later in Photoshop as you are already doing.

Hope that is helpful.

[ekim]

Everything that slejhamer said and also what colour is the wall around you. When you omni bounce with flash head pointing stright up the light not only bounces from the ceiling but from the walls around as well. This could cause the colour cast.

[JoeTampa]

Another suggestion: Shoot a frame of something white under the same lighting conditions (as long as it takes up most of the frame), then use the Custom White Balance function, selecting that image as the referent.