How to keep a colored object on a grayscale background

[Fernanda]

Hi, I ´d like help to do an effect: turn part of the picture in black and white and remain some part colored...someone can help me?

Tks!!

[Antonio]

- zoom your image on the part you want to remain colored.
- Use the polygon selction and select this part (use short lines)
- Close your polygon and set the menu Selection > Antialias > Progressive contour.
- Selection > Invert
- Apply grayscale

[Fernanda]

Tks a Lot Antonio...