How do I create a nighttime B&W image but have the subject illuminated by light in full color?

Question

I am trying to do something difficult. I am trying to create a nighttime black and white image, of a man walking down a road. I need the road and scenery to be B&W, but the man illuminated by a spotlight, and I need him and the spotlight area on him in color. "Blending" in Photoshop won't work. I don't want a ghost man, nor do I want a ghost street. And I want my colored man's spotlight to fade perfectly into the black and white scene, so the cheap B&W roses with red petals technique won't cut it.

I was thinking about using the multiple exposure mode in my camera, shooting the scene in B&W, and then switching over to color and illuminating the man for the second exposure, but my camera won't let me switch color modes between the two exposures.

So my only idea left is to use a single exposure shot in color, and after I'm done illuminating the man in the middle, slide a filter (or set of) filters in front of my lens, that effectively blocks out all colors, and my camera starts to see B&W and record the street as such. I don't think this is possible, though. I don't think you can turn light into B&W light.

Any ideas, guys? I'm beginning to think this isn't possible.

Answer 1

One option for blending/fusing two shots would be to take two exposures (ideally using a tripod), one with flash/spot on the man (and otherwise heavily underexposed), one without the flash/spot (exposed for the background, keeping the man still + dark to avoid layering colour over B&W).

You'd have to be careful to control the lighting in the area around the man, probably with off-camera lighting with 'barn-doors' or similar to really control the light spread and create a harsh shadow where you want the 'colour' shot to end.

If you need to take the shots in quick succession (e.g. if you need the man to be black in one shot and lit well in the other but otherwise in the same pose) you could use strobes that take a little time to recharge, so they simply fail to fire in the second (B&W background) shot so as to avoid illuminating the man.

No need to adjust the scene in the camera between shots, you can easily convert the background shot to B&W in post.

Then you're just adding the two shots together (the coloured section + blacked out section = colour only, the black background of the colour image + the B&W image lit up sections = B&W image only).

Answer 2

There is no way to put a filter on a lens to filter out colour and produce a black and white image.

Your best option would be to take a single photo with a regular camera and remove the colour from parts of the image using Photoshop (or similar image editing software). You don't have to blend two images together, you can simply select parts of the image and convert them to black and white (in Photoshop this can be done with the desaturate function).

Regardless, it will never look "real" because it is impossible to have a image which is part colour and part black and white without multiple exposures or digital trickery.