Making picture of campfire black and white, except where logo is overlayed?

[GJ999x]

Hi folks, def something of a newb here (i'm a music tech guy having to get a bit into graphic design world!) 

Not much more to add than the title - i have a picture of a campfire in color.  I have a logo that i can put on top of it (the logo png is black and white).  What i want to do is have the fire in B&W, and the logo visible only because the areas where the logo is are in color rather than black and white. 

Can anyone help with this? 

Many thanks!!!

George

https://linktr.ee/georgejacksonuk

[Ofnuts]

Assuming your logo has a transparent background:

• Duplicate the image layer and desaturate it (Color > Desaturate > Desaturate)
  
• Add a layer group
  
• Put the desaturated image in the group
  
• Insert the logo above it in the group (CAMPFIRE in the example)
  
• Set the logo layer to Erase mode.
  

   

Explanation: the Erase mode on the logo layer makes everything "in its shadow" in the same group transparent, so the result is a desaturated image with a logo-shaped hole in it, through which you see the original colors.

There is another solution, that creates a logo shaped color image over the desaturated image.

[GJ999x]

Well, that's sorted, thank you so much!!!!  Incredibley helpful, i miss when the internet felt like this in general!!  

Have a great day!! 

George