Flash Placement

I work for a counter top fabricator and we recently purchased some software that allows us to lay our CAD work over a digital picture to see what a kitchen layout will look like.

The problem that I'm having is that I can't seem to get even enough lighting over then entire slab of granite. We're using a Rebel XT camera and have 4 Alien Bee 320WS B800 flash units with shoot through umbrellas.

The camera is 16' back and 6'8" up from the floor. Each flash is about 4' out from the edge of the table and about 5' in front of it.

Is there some kind of suggested angle that the flash is supposed to be in relation to the face that would help remove the hot spots on the edges?

http://i38.photobucket.com/albums/e1...s/100_2601.jpg
http://i38.photobucket.com/albums/e1...res/test14.jpg

Hey Brian, I'm no studio expert but I can tell you that your not going to get much result shooting "through" those umbrellas as you have the black covers on the insides. Ahh, correction. . .it seems from your pictures that the black covers are surrounding the head and used to keep light from bouncing back.
I would think that for a large countertop subject you would be best using two large (60 ") bounce umbrellas, one on each side.
Using what you have, I think bouncing as opposed to shooting through might avoid the "hotspot" that can occur in the center of the shoot thru umbrella. Place them as you have them, but place the black covers on the outside of the umbrellas and turn the mounts around so that the light bounces off the insides of the umbrellas and to your subject.
As I said, no expert here and maybe someone with more experience will jump in here . . .

Quote:

---

Originally Posted by Brian_Stone

Is there some kind of suggested angle that the flash is supposed to be in relation to the face that would help remove the hot spots on the edges?...

---

Hey Brian, welcome to the site...

Gary touched on what your problem might be. What it comes down to is that you're using four not-so-powerful lights with small shoot-through umbrellas to try to light a relatively large surface evenly.

Tough to do...

What you have with this setup is essentially four small floods lighting from the side. You're almost always going to get uneven light this way.

What Gary suggests makes sense. You'd get much better results by bring the lights out in front of the subject and bouncing them into larger umbrellas. With four lights, you probably wouldn't need 60" umbrellas. 45" or so would likely work fine.

If you don't want to buy more gear, and get more illumination from these lights as well, I'd suggest creating cheap pvc light panels and shoot through them, two lights on each side.

But this leads to another problem: the lights being in the shot if they're out in front. Reading what you describe, 16' seems like an awfully long distance for the camera to be away from the subject surface.

I'm thinking if you use a wider angle lens so you can move the camera much closer to the subject, your lights can be out in front more but to the sides (or maybe just slightly in front) of the camera so they don't show in the shot.

This would then be a pretty typical setup to light a large area evenly.

Hope that helps...

Quote:

---

Originally Posted by Asylum Steve

But this leads to another problem: the lights being in the shot if they're out in front. Reading what you describe, 16' seems like an awfully long distance for the camera to be away from the subject surface.

I'm thinking if you use a wider angle lens so you can move the camera much closer to the subject, your lights can be out in front more but to the sides (or maybe just slightly in front) of the camera so they don't show in the shot.

---

The reason for not using a wide angle lens is that it would warp the image too much. We need the slab to appear perfectly flat so that when we lay our CAD work over it, it is to scale. That's actually the reason we have the panels with the dots. The software picks up the dots and automatically adjusts the images to compensate for the lens. I just don't know how much it will compensate and what quality the image would be after that.

I'll try shooting into the umbrellas instead of through them first. If that doesn't work then I'll think about moving the camera.

Quote:

---

Originally Posted by Brian_Stone

The reason for not using a wide angle lens is that it would warp the image too much...

---

Brian, I can see how that would be a major concern, but there are wide angle lenses that do not distort. It's only super wide lenses that cause a noticable bending.

Perhaps wider is a better word to use. IOW, something shorter than what you're using now so you can get closer, but not so short that it distorts...