I want to make an image black and white, except for one specific color, e.g. purple. I know the technique where you use two layers and the history brush tool, but it consumes to much time and the result is not very precise. I've heard about a way where you use two layers and choose the color you want to bring out.

I would be very thankful if anyone could help me with this technique.

Ole-Chr.

try > select > color range > layer via copy, then turn the backgrond to b/w

Don't think in black and white: think in the colour of your heart...

http://www.youtube.com/watch?v=aS0yRaq8s-c&feature=PlayList&p=B131D120F86A23D4&playnext=1&index=53

Its a famous song in Holland.

^^^What Splodge said.

Well here is one way but it will depend on the colors of the image to start with. I chose a colorful image and chose to keep blues and purples while turning everything else to BW.

Start by converting the image to LAB color.


Set up a hue/Saturation correction layer and turn the saturation to -100.


Bring up the Layer Options palette and and modify the blend if sliders as follows. Select the b channel from the drop down menu. Move the slider as indicated. Use the option/alt key to split the sliders as indicated.


Here is my final result as a before and after gif.


Maybe this will work for you too?? There is no masking required and this took me less then 30 seconds to complete.

Give it a try!

You can get some nice effects bringing out the colour on only one object

wow, cool lesson

I was gonna suggest blend-if but I see the wise Jerry beat me to it.

I did this (quick and dirty) using a desaturated layer above the full color and then masking.

Original

a tut from the master himself...listen kids!

You can always convert to black and white and then back to CMYK/RGB and then...

either...

add a purple as a monotone if you want it all over

or...

add a new layer, fill with purple, change the layer to 'color' and adjust/paint as required...

or...

what the others said!

nice

I would just make the adjustment by dropping the saturation out of the undesired colours with the 'hue and satuatution' in the colour options, its quick and easy, but does depend on the picture you are changing.
You have 6 colours to adjust Red, Green, Blue, Cyan, Magenta and Yellow.
Purple usually comes under Blue or Magenta.

Play with it and see if it effects the photo in the way you want.



Hope it helps