The mysterious Lab colour space 🙂 Firstly, let me suggest that if you really want to know about the Lab colour space you get your hands on anything by Dan Margulis. He is the guy the gurus go to when they want to know something about it, he’s the man.

A quick way of looking at the Lab colour space is this

L = Lightness

a = Red and Green.

b = Blue and Yellow.

Using a curve in the a or b channels can enhance specific colours in specific directions. Using a curve in the L channel only affects the tone of an image without affecting the colours.

Having said all that, we’re not going to be using curves, we’re going to apply a specific channel (using the apply image command) to get a desired result.

The image below is from and I can’t find the owners info, so please don’t go splashing it around the web. The image below the start image is a comparison of the start and finish images. The original image is ‘as is’ I have done no corrections to it all other than resizing it to a manageable size for this tutorial – 800 x 571 @72dpi.



Just before you get going. The settings I’ve used on this particular image may not work well on other images. You’ll probably have to fiddle around with different settings, blend modes and opacities to get the look you want. I call it playing 🙂

Open an image, duplicate it and then close the original. Double click on the b/ground layer to unlock it and either choose the default name or call it something deep and meaningful, then duplicate the layer. My 2 layers are called ‘Layer 0′ and Layer 0 copy’

Working on the top layer go to Image>Mode and click on Lab colour – see image below. Once you do that, you will be presented with a dialogue box asking if you would like to merge the layers. Politely decline.



Now you’re in the Lab colour space …… Next, go to Image>Apply Image and you will be presented with the dialogue box below. Some of the settings might be a bit different.


Taking a look at the dialogue box – the source will be the original b/ground layer, which in this case is Rusty Car Copy. The Layer drop down menu is for the layer you want to apply the effect to – in this case the layer 0 copy layer. The channel drop down menu will give the options of Lab (which is a combination of Lightness, a and b) – or L,a, b channels individually and transparency is the last one. The blending option is familiar to most of you and so is the opacity setting. This is where you get to player with the different options, except the Source and Layer menus in this case. So you can go ahead and punch in the numbers I have if you like, or experiment a little bit to something you like.


Once you have the settings are you want them, go to Image>Mode and choose RGB from the menu, politely decline the invitation to merge the layers and you can proceed as you wish. Go ahead and change the blend mode of the layer, use a mask to reveal or hide parts of the colour enhancement ….. but most of all, have fun 🙂

And here is the finished image.