advanced photoshop
Jan
19

How to use Photoshop’s LAB Color Mode

Posted in:
Tips & Tutorials, by The Advanced Photoshop Team

Discover the awesome power hidden in LAB Color and give your digital images a colour boost using the tools in Photoshop

What is LAB Color? How can LAB benefit you as a professional digital photographer? How does LAB differ from RGB and CMYK?

These are just a few of the questions that many people ask when faced with LAB Color for the first time, and for this reason it is often overlooked. This tutorial will give you a simple description of what this colour mode is all about and how you can use it to professionally enhance your digital artwork.

For high-end professional digital artists LAB Color is what you might call the final lesson in making your images’ standard of work shine from the rest. It is often said that no matter how good at photography you are, and no matter how expensive the camera you use, every image can benefit from a little bit of LAB attention.

This tutorial does not confess to teaching you everything about LAB; it is so complex that there are whole books dedicated to just this one aspect of colour. Our aim is to first introduce you to LAB if you haven’t heard of it before, and, if you have, we will brush the surface and run through a tutorial showing the kind of benefits you can gain from mastering only a small element of LAB Colour correction. In this example we are using an image that allows us to demonstrate the use of curves and channels on fine texture – in this case sand.

The original image is by no means poor, but you will see after a few simple steps even a seemingly perfect image can be improved!

Step 1: Why this image?

Step 1

The first step is to open the image that you wish to adjust. This image has been selected due to the fact it has some great sand detail to demonstrate the LAB correction in action. However, you can also follow this tutorial with your own images.

Step 2: Duplicate for comparison

Step 2

To the untrained eye the changes you are going to make by following this tutorial are very subtle with each step and you’ll want some way of seeing what you have done. It is a good practice to make a copy of the original image so that once you have finished you can compare your alterations. Keep both versions open so that you can switch between the two easily and quickly.

Step 3: Change mode

Step 3

Minimise the original image and just leave open the one that you are going to work on. Now you have your image open you need to switch to the LAB Color mode. To do this, go to Image> Mode>Lab Color, which will automatically convert the image. The picture will look no different at first, but the identification bar at the top of your image will display ‘Lab’.

Step 4: Introducing curves

Step 4

In this tutorial we are concentrating on the Curves and Channels, so the next thing you have to do is bring up the Curves dialog box. You can do this by going selecting Image> Adjustments>Curves from the menu.

Step 5: Customising the settings

Step 5

The LAB default settings in the Curves dialog box need a touch of refining before we begin. By clicking on the arrow in the middle of the lightness to darkness gradient make sure the lightness is on the left-hand side.

Step 6: Change the percentage

Step 6

The next thing to customise is the percentage intervals of the gridlines. The default is set to 25 per cent increments. This will cause changes to be a little too coarse for our image, so Alt-click on the grid and toggle the lines to 10 per cent intervals instead.

Step 7: What are curves?

Step 7

If you are unfamiliar with curves these allow you to make precise adjustments to the entire tonal range of an image. The tonal range is represented by the diagonal line on the grid, highlights at one end and shadows at the other.

Step 8: Change to Channel A

Step 8

Click the word Lightness and select ‘a’. With the cursor grab the top anchor and move it until it has the value of Input 85 and Output 100. You will see immediately that the image will turn a green tinted colour.

Step 9: Adjusting the curve

Step 9

Now it’s time to adjust the bottom anchor point. Set this to Input 15 and Output 0. You will see that the middle of the tonal range now crosses the centre point again removing the tint.

Step 10: Switching to Channel B

Step 10

Select the ‘a’ and change it to the ‘b’ menu item in the Channel drop-down list. Repeat the exactly same process for ‘b’ as you did for ‘a’, setting the top anchor to Input 85, Output 100, and the bottom anchor to Input 15, Output 0.

Step 11: Select the Lightness

Step 11

Now go back to the Channel drop-down menu and select Lightness. If you click your cursor on the actual image now you will see a little circle appear on the diagonal line. This tells you where that particular colour appears on the tonal range.

Step 12: Increase the contrast

Step 12

Drag your mouse around your image and see the circle move in the Curves dialog box. You will be able to clearly see the range that the sand detail occurs in. Here, by making the gradient of the line steeper, you will bring the contrast out in the sand and increase the level of detail.

Step 13: Get steeper

Step 13

To make the tonal range of the sand steeper, simply click on the middle point of the diagonal line to create a new anchor point and drag it across the grid. The value of this new anchor point should be Input 55 and Output 60.

Step 14: The Channels palette

Step 14

Click OK in the Curves dialog box to commit to the changes and select Windows>Channels to bring up the Channels palette. Three channels are present;: Lightness, A and B. Select Lightness show the Greyscale Lightness image.

Step 15: Unsharpen Mask

Step 15

With the Lightness layer selected, go to Filter>Sharpen>Unsharpen Mask. The Filter dialog box will appear. Set the following values: Amount 200%, Radius 1 pixel and Threshold 10 levels, and click OK.

Step 16: Convert image to CMYK

Step 16

Now reselect the LAB layer from the Channels palette to display every Channel again and a full colour image. We’re done adjusting the image in this mode and it is time to convert the image for use in projects or sending to clients. Therefore, the last step is to convert your image to CMYK by selecting Image>Mode>CMYK. Now save your image as a TIF file.

Step 17: Time to compare

Step 17

On reviewing the altered image you may not see much of a difference straight off, as it is quite subtle. Instead you should and compare it against original image that you left open in the second step. Now you should be able to see that the image has become more vibrant and sharper.