Paul C. Buff, Inc. Technical Forum

Please help with this:
QUESTION 1:
On location how best to light 9 feet tall by 15 feet wide tall white backdrop evenly.

I have 4 Einstein and 1 B400 and canon 580 flash.

Earlier I used two Einsteins with 48 "white umbrella (covered black). The sides of backdrop becomes very hot if i have to spread light to middle section.

Will 2 86" white PLM With black back and Umbrella reflector will light evenly or

4 51" white PLM With black back and Umbrella reflector.

I cannot mix B400 with this as this is for shooting contemporary dancers, they are are all over the space and may affect freezing them. some sections of the backdrop is not white enough and some parts become extremely hot and spill light into them.

I need one light as main and another as fill also

QUESTION 2
Does 51" white PLM With black back and Umbrella reflector will give more spread or 48-inch Translucent White Umbrella With black back and Umbrella reflector.


I appreciate any suggestions
:)

First, a white 51" PLM with a black outer cover vs. a 48" white shoot through with a black outer cover will be so similar as to not really be distinguishable.

Generally, to light a large area like that, I recommend cross lighting. This means the light on the left of the background is aimed at the right. The light on the right is aimed at the left. You can avoid hot edges by feathering the lights across them.

Distance will be your friend here. The further away the lights are from the edge of the background, the more even they will be. A little forward of the back ground (but not so far forward they are on your subject) and off to the sides. Being farther away, they will be less bright, so you will have to increase their power (or your ISO), but they will be more even.

I often do shoots with 12' backdrops and I use 360Ws lights on either side with barn doors (to keep light off the subject an out of my lens. I rarely have the space to pull them out as far as I would like (the stands are generally on the BG paper), but I get pretty good coverage. I get a little darkening in the corners, which is easy to edit in post, but I get the amount of light on the paper where I need it. If I could move the lights back, they would spread sufficiently.

Also, as far as the amount of light on your background, your main and fill will contribute to this to, most likely.

Thank you so much. It helps me a lot. One last question:

Does 2 big modifiers (86" PLM) will be better or 4 (51" umbrella) for spreading light to the backdrop

Again, I usually use 2 lights with barn doors. If the budget allowed, I would use 4 lights with barndoors. However, 4 white 51" PLMs would probably be better than 2 86" PLMs, if for no other reason than you have twice the number of lights, and presumably, twice the amount of power. Also, 4 lights can criss-cross better (i.e. lower left to upper right, upper left to lower right, etc.).

If possible (and if you have not already), set up what you have and see how well it works before investing in new equipment.

Thank you so much. I appreciate this great help. For long time, I couldn't figure out how to solve this problem. But now I will be on the right track. Much appreciated.

How useful would a pair of background reflectors (e.g. http://www.paulcbuff.com/ubr.php ) be for lighting something like this? Or are they intended more for putting a "spotlight" or "halo" on the background?

I guess if enough effort was put into it, you could use them. However, they were more intended for a halo, as you describe.

I like the barn doors, since you can aim across the back drop, but flag any stray light coming forward to the subject or in the lens.

Also, it is a rampant "rule" or suggestion the background needs to meter 2 stops or more than your subjects. If your backdrop is white, a properly exposed backdrop will be white. Now, in practical terms, most are near white, and/or may have some ripples, creases, mars, or other texture that may create isolated darker areas. There is nothing wrong with over exposing a touch to get the texture out or to bring to a true white.

By over exposing too much, the background then becomes a significant source of light and cause flare in the camera, and haloing around the subject. Also, highlights on the subject from the background may also blow out.

Lastly, don't forget the main and fill lights will contribute to the background exposure. So you will want to meter the background with all lights, and the subject with main and fill (you can fire the back ground lights as well, but they probably won't contribute to the meter reading).

My main light is 86" Silver PLM with front diffusion cover and fill light is 64" silver PLM with diffusion fabric . Possibly they were adding light to the background too. I was getting halo on the dancers. Its going to be better now. It was a great help in solving this problem. I want to thank you for this help.

Regards,
Kamal