How to make a red square with light on a white background?

[brandon_andreadakis]

<p>Hello, <br>

I am doing a shoot for a hair coloring line whose symbol is a red square. For at least one of the shots, I want to have a red square in back of the models head, created solely with light, on a white background. How do I do this? I don't necessarily need perfect edges to the square. <br>

If I can't do this with light, do you guys think that taking a red posterboard and dangling it with filament in front of the white paper would work?</p>

[lornesunley]

<p>use a strobe with a red gel, cobble up a modifier/snoot that throws a square shape.</p>

[mike dixon]

Projecting a red light onto a white background won't produce a red color. If the background is a fully-exposed, "true" white, it doesn't matter what color light you add to it, white is white. If it's not completely white, you might get a very unsaturated light pink.

 

Taping a red square to the background is probably the easiest way to get the effect your describing. Suspending red posterboard behind the model's head could cause issue with shadows on the background, depending on your lighting.

[brandon_andreadakis]

<p>Thanks Mike! That makes sense. Even with taping the posterboard, I'm going to get shadows and it will lighten the posterboard cause it's going to get the same light as the background. I'm shooting the model with a ringflash, so shadows would be a problem.</p>

[stamos]

<p>If you may use edit then shoot with all red background, expose carefully the background and later with photoshop mask the area you want to be white. It would be easy mask because the difficult part are the hairs that will remain over red background. If you may not do this then may you use a big TV/monitor as background?</p>

[mariosforsos]

<p>Another way would be to use a projector, placed probably somewhere higher up, displaying exactly what you want onto the background.</p>

[brandon_andreadakis]

<p>Stamoulis, that's a great idea. That is what I am going to do. Thank you! </p>

[henryp]

<p>Two backgrounds. The one nearer you is white with a square cut out. Behind that is a red background illuminated with a red gel.</p>

<p>Henry Posner<br /><strong>B&H Photo-Video</strong></p>