How to get coloured background lights and foreground person in creative portrait shootings exposed equally?

Question

Let's say I am shooting indoors in a small room. I have some lights in the background, like an LED strip, without much possibility of changing them around. Now I want to photograph a person in front of the LED strips and I want them to be properly lighted while also having the colour from the LEDs show up in a way that makes sense. I want to use a 35 mm lens and I don't have too much space to work with, like maybe two meters max between the background and the person in the foreground.

Various dilemmas I am facing now:

• If I want the lights in the back to look good, I need to reduce ambient light as much as possible
• This means the person in the foreground is not lighted properly, so I need to introduce a different light source for them
• Putting a flash and a small softbox close to that person (not even thinking about fill lights etc.) means that I need to introduce more distance between subject and background so that my key light does not end up overpowering the background lights
• Putting in too much distance means my 35 mm ends up showing too much of the background, including parts that I don't necessarily want to capture

Switching lenses is not an option in this case due to space restrictions and the general look I want to achieve. So how do I approach this best? I considered the following solutions:

1. Buying a beauty dish to use as my key light and hoping that with a honeycomb grid the light fall-off would be quick enough to not really reach the background
2. Using some form of exposure bracketing and fixing everything in post

I am really not too fond of 2, so would 1 be the magic bullet that's going to solve my issue? Or is there a different approach I have not considered that would solve this as well?

Answer 1

Putting a flash and a small softbox close to that person (not even thinking about fill lights etc.) means that I need to introduce more distance between subject and background so that my key light does not end up overpowering the background lights

There is no reason why your added subject light (key) should overpower the BG light. It would have to reach the BG at a high enough power as to reflect back stronger... which of course means your subject would be completely blown out.

You need to lower the power of the key light (power setting, additional diffusion, ND filter, etc) so that it doesn't reach the BG at a high power, and place it close enough to the subject that it is sufficiently bright there.

I.e. let's say the subject and BG are both white things of equal reflectivity, and your key light is 2ft from the subject providing a proper exposure; if the BG is 2ft behind the subject the BG would be about 2 stops underexposed *due to the inverse square law (double the distance, 1/4 the light power).

A BD w/ honeycomb won't reduce the flash power reaching the BG, it reduces the spread... if that's part of your issue you can add a flag to the key light.

*close enough anyway

Answer 2

Flag, or V Flat between your person and the background, and as previous answer grid will help with spill.

Maybe barn doors on your lights too for even more control.

But look at flagging, really good when in small spaces:

https://slrlounge.com/photography-tips-how-why-to-use-flags/

solid flags are used to block light. If you need to cut the light from a portion of your image entirely, this is the one you want. .. demonstrates this by blocking the background from being lit by his key light.

https://theslantedlens.com/2018/shaping_light_with_flags/

Using Flags to Kill the Background For this setup, we used a solid flag close to our light source to control the spill of our light. We didn’t like how the light made our scene one exposure. The flag was placed on the corner of the frame, just near our subject’s hairline.

https://www.diyphotography.net/lighting-technique-flagging-feathering/