The BEST way to convert a colour image to Greyscale in Photoshop

You will probably read this blog title and think ‘Well, I already know how to change an image to greyscale and it’s easy as pie.’ But are you doing it the right way? The best way? The GGS way?

Until recently, I most definitely wasn’t. In the world of design it’s our responsibility to create beautiful looking designs and most of the time we’re handed a selection of images on a plate. The advantage of working at GGS in Norwich is that not only are we designers, but we are photographers too – so when our photographer asked me to change some images to black and white for him, he ensured I did it the ‘right’ way. And it definitely made all the difference! Using this Photoshop tip ensures your black and white images pop on the page and stand out. They will complement designs and appear beautiful on the page.

Of course this is just one of the many ways of changing an image to black and white in Photoshop, the simplest of course is to change the colour mode to Greyscale. But WARNING – this will simply remove all colour information and leave you images look flat with low contrast. This Photoshop tip is a sure fire way of getting the best out of your new black and white images.

Convinced yet? Here’s our Pro Photographer’s Photoshop tip of ensuring great quality black and white photos…

1. Open your image in Photoshop & change the Colour Mode

Once your file is open in Photoshop you will need to change its Colour Mode. You can do this by going to ‘Image’ in the menu followed by ‘Mode’ and then you want to select the option which says ‘Lab Colour‘.


2. Open the Channels Palette

For this step you need to go into the ‘Channels‘ Palette. This can be accessed via ‘Window‘ and then down the list to ‘Channels‘.

You should now see a list in the ‘Channels’ window. One item will be ‘Lab‘ which shows you the colour image, the other will show you a ‘Lightness‘ layer and then there should be an ‘a’ for A Channel and a ‘b’ for B Channel which will appear greyed out. As you click between these three you will notice some changes to the image. As you can see here:


When looking at an image in LAB mode in Photoshop you will see these 3 layers working together in the Channels palette. The top channel ‘Lab’ shows all channels blended to create the colour image – and below where it is split into the other 3 channels of Lightness, Channel A and Channel B.

The Lightness Channel holds info for how light and dark the image is.

The A Channel is a scale of information from Red to Green.

The B Channel is a scale from Blue to Yellow.

Using Lab mode in Photoshop gives you a much greater range of colours compared to RGB or CMYK. It is based on how humans see colour with a combination of brightness, darkness and how much colour there is on each A & B axis.

3. Now select the ‘Lightness’ Channel & Delete the rest

In this case we’re focusing on making a black and white image so we’ll be using the ‘Lightness’ Channel which is the data made up of light and dark. Now you want to make sure that the ‘Lightness‘ channel is the only one we have left. Delete the A and B channels by dragging them to the Delete icon. This should leave us with just one channel labelled ‘Alpha 1‘ or similar.

The benefit of using this Lightness Channel is that rather than simply converting each pixel to a shade of grey like you would by using the Greyscale method, by using Lab Colour Mode, Photoshop makes a more realistic gage of the whites and blacks in the image. It gives the image a much better contrast.

4. Convert your image to Greyscale

You should be left with just one channel in your channel list but to ensure that this image can be used in multiple formats for both print and web, it’s best to convert your image to greyscale.

Simply go back to ‘Image‘ and then ‘Mode‘ at the top and select ‘Greyscale‘ as your new colour mode. Visually, nothing should change but it is important that the final file you end up with has no colour data in it.

And there we have it!

This may seem like a convoluted method of achieving a black and white image but the results are definitely worth it…

The only difference between these two images is that the left is done by simply changing the colour mode from RGB to greyscale and the right is achieved through the method we’ve given you above. By using this Photoshop tip, this will create a far superior and more dramatic looking image – as opposed to the simpler method which leaves the image looking flat

Of course you have got the option to use Levels (Image > Adjustments > Levels) even after the process to boost the blacks and whites in your image but this completely depends on what kind of finish you are going for and of course the image you are using. In the examples below we’ve used the Lab Colour method and Levels after to really give these portraits impact.

But don’t take our word for it, try it with some of your own images and see the differences for yourself!

Share with the world!