Lighting advise needed.... desperately!

I am hoping that the experience in this group can help me. I have been taking outdoor portraits for two years now. I love shooting outdoor, but I am at the mercy of mother nature. I have umbrella light (4 of them), and two head lights and have done some indoor shoot with white and black backgounds. For a while I did fine, now I am getting a dark background and a yellowish color. No matter what I do i can't seem to get that beautiful white, shadow free background that I see on so many of the awesome photos that I see in the forum! My kids are so tired of practicing with me but I would NEVER ask someone else to bring their children over for nothing. I have an appointment with a friend here who has a thriving photo business to see how she does it, but she has the most amazing studio with lights that hang from the ceiling. I am so not there yet.

Is there any advise that you can give me that will help me learn how to do this correctly????

Well, chuck gardner's tutorials are very helpful: http://super.nova.org/​DPR

I would suggest that you have your subjects seperated from your backdrop, and position your key light above your subject so that the shadows are directed downward. You can also position a backdrop light right behind your subject directed at the backdrop. That should eliminate the background shadow, and I am guessing that your color cast might be your white balance

Same white background - different looks

More of his white seamless tutorials

'Yellowish background'?! Are you lighting witn incandescent light? If so, that is a color balance problem. You can't mix incandescent with electronic flash well, unless you use color compensating gels to make one of the lights 'appear' like the other, then use a suitable WB setting (or postprocess)

Normally, 'underlit' would result in a neutral grayishness rather than pure white. That would be fixed with more light intensity on the b/g

Wilt wrote in post #7580648
'Yellowish background'?! Are you lighting witn incandescent light? If so, that is a color balance problem. You can't mix incandescent with electronic flash well, unless you use color compensating gels to make one of the lights 'appear' like the other, then use a suitable WB setting (or postprocess)

Normally, 'underlit' would result in a neutral grayishness rather than pure white. That would be fixed with more light intensity on the b/g

A different question for the OP along the same lines: Is your background light actually firing? You mention four umbrella lights, which I take to me studio-type lights. If they are strobes rather than hot lights, they probably have modeling lights. And if the strobe isn't firing, you'll be exposing the background with the modeling light. That will get you an underexposed and yellowed background.

Rick "been there, done that" Denney