Converting to mono using LAB mode

Presented by Pixalo - Submitted by Rob Barron

This is one of my favourite methods of converting to black and white and I know a few others I have shared this with have said they now use it a lot so maybe it will be helpful to some others. This has been covered by Steve before but I have added an extra step so felt it worth adding here. I hope the screenshots included will help clarify anything if I have not been clear in the text.

The beauty of this method is that it gives you lots of control to get it just how you want it, The reason it works so well is that the LAB mode adjust luminance or light levels rather than levels of RGB.

This is dead easy so just follow the steps and I assure you this will prove very useful.

I am using CS2 but CS1 and below will work fine.
Step 1: Open picture you want to convert (ok, I know that was obvious but hey!)

Screenshot shows colour picture in normal RGB mode with RGB channels.

Step 2: Under Image > Mode select 'Lab Color' (this won't change anything as yet)

Screenshot shows here to find Lab Mode:

Step 3: On the Layers palette you have another tab called Channels. Click on this. Now you can see the first difference: Instead of the usual RGB channels, we now have four channels, the first is the usual combination of the other three. Then you have 'Lightness' and an A and a B channel. You will see the thumbnail of 'Lightness' is mono and this is the only channel we need. Select this channel and you will see your whole image is now greyscale.

Screenshot shows the new channels: Lightness, A and B

Step 4: We are now going to change the mode back to grayscale. (Images>Mode>Greyscale) PS will ask if you want to discard the other layers. You do so click ok.


Screenshot shows image now, a bit too light!

Step 5: Ok, so now we have a greyscale but chances are it is a bit light. So let's sort that out...
On the layers pallete, select the (only) background layer. Press Ctrl+J to duplicate this layer.

Step 6: With the duplicate layer selected, change the blending mode to 'Multiply'.

Screenshot shows duplicate layer added and blend mode changed:

Step 7: This might be ok but is probably a bit dark but here is the bit where you can control exactly what level you want. Just adjust the opacity of the second layer down to the point where you get the balance of light and dark you want.

Screenshot shows opacity adjustment:

Step 8: If you need to, get as close as you can with opacity, then press Ctrl+E to merge this back into one layer. Now using curves, you can adjust it further if you need to. Most times you won't need to though.

Here is the final shot duly adjusted:


There you go, I hope you find it as useful as I have. As you know there are loads of ways of going mono but I found this method in Scott Kelby's superb book called 'The Photoshop Book for Digital photographers' and if you haven't got it, get it! It's brilliant and written beautifully so that even the most difficult of tasks seems easy.