Looking at the photos and having read the Zack Arias info I would assume that you need to move your subject light further away (higher) from your model. This would make the difference in the amount of light hitting the model vs the floor much closer. You could also feather the light by aiming it down a bit if you needed more light on the floor and less on the models head.
Thanks, guys! If you saw my UPDATE in the post in this thread, you'll notice that I finally found a formula that works for my studio. I started this thread months ago when I was trying to figure out how to do this. I recently updated the thread to show the adjustments I'd made in case it was helpful to others. Appreciate your comments!
ereza: I looked into the lasolite but you have to have your model really close to the background and if you try to shoot at any angle you lose the background and have the studio showing right or left; I wanted to use the wide paper rolls for this reason. Nice product though, thanks!!
David: one of the things I did was change my umbrella arrangement which created more even lighting, and that did help.
Beverly Guhl wrote:
...It turned out to be a WB issue actually. ...Once I realized my camera shoots warm and started using a gray card I don't have the problem anymore.
Yep; that's a problem that can sneak in.
On well-lit whites it doesn't show so much, but as the light intensity falls the off-white character becomes more visible.
In your first shots from back in February with the subject being lit from above but close to the head, the light fall-off from head to floor was enough to really show the color cast (that old inverse square law bugaboo). By lighting more evenly top to bottom, and by getting the WB correct from the start (gray cards or color meters are great tools), the problem is a lot easier to handle.
Future Man wrote:
I just realized there's a faint pink cast at the top of my photo.
I had two White Lightnings hitting the background (a somewhat dirty white wall) with an Alien Bee in a beauty dish on my model.
Was I probably just not hitting the wall evenly with the White Lightnings?
I noticed in my own tests that when I didn't get the light evenly hitting the background, the falloff would not be white since it's therefore more underexposed. My own tint seemed to be a white balance issue.
A lot of times your "white" surface won't actually be white, especially when it's not seamless, and it'll also be really unforgiving of inaccurate white-balance where it starts to fall off. I've noticed that my studio's white cyc is actually a little on the warm side, and it's especially evident when I'm not trying to blow it out. This was just one light, for instance, and white-balanced to a grey card (white balance adjustment is the only editing on this):
You can also see the telltale dark line in the arc of the sweep, since that's effectively the furthest thing from the light source. I don't mind it, as I feel it gives a spatial reference cue much like a horizon does, but it's frustrating when you don't want it there.
Future Man wrote:
I just realized there's a faint pink cast at the top of my photo.
For some shoots, the colors of the clothes or other subject have to be exact, so using a calibrated color meter or setting WB from a gray card is called for. But for portraits and many other shots, the exact color of the subject isn't as important as the overall feeling. In that case, if you're going for a white or neutral-gray background, you can set a custom WB off the background itself under the lighting to be used, then bring in the subject after setting the WB.
You may still get variations in tone on the BG, but you shouldn't get too much of an overall color cast.
If you're getting localized color casts, look for nearby colored objects (including walls, ceiling, decorations, etc.) reflecting light onto the set.
