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Transcript for Improved Saturation with LAB -- Part I

Transcript by Ron Bigelow

Photoshop CS4 Used in this Tutorial

Welcome to the Ron Bigelow Photography LAB Saturation video. Today, we are going to look at a technique that, in many images, produces superior color saturation. Now, we are all familiar with adjusting the saturation of images. We generally use the Hue/Saturation adjustment that we find on the Adjustments panel. Usually, this works just fine. However, there are exceptions. With some images, the color just doesn’t seem to come alive. When this occurs in images where the color is a major factor in the success of the image, the image losses much of its impact.

The image we have here is a case in point. This image was shot in a rainforest shortly after a rainstorm. The vegetation was a lush, beautiful, saturated green under an overcast sky which cast a soft light over the forest. When I was there, I was enamored by the beauty of the forest. A very large part of that beauty came from the stunning, saturated foliage. For this image to be a success, we need to bring out that same feeling of beauty for the viewers of the image. This can only be done if we can recreate that lush, saturated forest environment.

Right now, the image doesn’t communicate that beauty. The colors just do not seem alive. Let’s try increasing the saturation by moving the Saturation slider to the right. That resulted in some improvement, but frankly it still looks rather lackluster. We could try moving the Saturation slider farther to the right, but the image starts to look over saturated. In addition, the green simply isn’t coming alive. Let’s finalize this at a setting of about twenty.

So, we have a nice shot, but the colors just haven’t come alive. This is the time that we move to LAB saturation. So, let’s carry out the LAB saturation on this image and see what we get. Here is another copy of our Rainforest image. We need to convert this image to the LAB color space. We could just move this image straight to LAB. However, let’s make a duplicate of this image by choosing Image/Duplicate. We will convert this copy to the LAB color space. The reason we convert the copy, instead of the original image, is that this workflow will give us more flexibility as you will see later. To convert to LAB space, we choose Image/Mode/LAB color.

Right away, we get a warning. This warning indicates that we have run into our first limitation of the LAB saturation workflow. Moving in and out of the LAB color space can cause changes in the appearance of Smart Objects. Since the layer that we are converting is a Smart Object, as shown by the Smart Object image on the layer, this could cause problems. So, we need to rasterize the layer so that it is no longer a Smart Object. To do this, we just click the Rasterize button.

We are now in the LAB color space. However, before we jump into our edits, I would like to mention a couple of points about LAB. First, it's important to know that LAB is a very large color space. In fact, LAB is the largest color space. Of significant importance is that LAB includes every color that the human eye can see.

The next thing that we need to know about LAB is that LAB has three channels. However, these channels don’t look like the channels that we are used to with the other color spaces. With the other color spaces, each channel represents a specific color. As an example, let’s go back to our original image for a moment. This image is in an RGB color space. Looking at the channels, we see that, with an RGB color space, we have three channels: a red channel, a green channel and a blue channel.

Now, we come back to our LAB image. Moving to the channels, we see that we have three channels: a Lightness channel, an a channel, and a b channel. Let’s take a look at each of these channels. The Lightness channel is easy to understand. This channel represents the Lightness or tonality of the image. It has no color information. Now the a and b channels are a little more tricky to understand. These channels do not represent a single color, like the channels in the RGB color space. Instead, each of these two channels represents a range of colors.

The a channel represents the green-magenta color continuum. Let’s see what that means by launching Curves. When we click on the Channel menu, we see the three LAB channels. Let’s choose the a channel. Now, the left side of the channel represents green. Watch what happens if I move the black point slider inward. The image became extremely green. Let’s try moving the white point slider inward. The image became extremely magenta.

The b channel represents the blue-yellow color continuum. Moving the black point slider inward causes the image to turn blue. Moving the white point slider inward causes the image to become yellow.

Now that we understand the LAB channels, let’s use the LAB color space to increase the saturation of our image. Actually, the process is very simple. We simply move the black point and white point sliders for the a and b channels inward. Since we are already in the b channel, we can start here. We start by clicking the black point slider. Now, it might seem logical to just move the black point slider to the right. However, I am going to type a value in the box instead. You’ll see why in a second. Let’s leave in the negative sign and type in 76 so that we get a value of -76. You can see that the black point slider moved inward.

Before we move on, it is important to understand what we have just done. Look at the Input and Output boxes for the Black point slider. What this tells us is that a value that used to be -76 is now -128.

Next, let’s click the white point slider and type 76 in the Input box. Look at the Input and Output boxes for the white point slider. What this tells us is that a value that used to be 76 is now 127.

Okay, let’s make sure that we understand this. What used to be a range of color from -76 to 76 on the blue-yellow color continuum is now a color range from -128 to 127.

Also, notice that I set the black point slider to -76 and the white point slider to 76. This is because we need to move in both sliders an equal amount. If we don’t, we will end up with a color shift. Using the boxes, instead of moving the sliders, makes it easier to input the same numbers.

Next, we go to the a channel and do the exact same thing: set the black point slider to -76 and the white point slider to 76. Again, it is critical that we move these sliders inward the exact same amount as we did in the b channel. So, what used to be a range of color from -76 to 76 on the green-magenta color continuum is now a color range from -128 to 127.

Have you figured out what we did yet? By using the a channel, we were able to stretch out the colors along the green-magenta color continuum. This increased the contrast between the colors. Similarly, we were able to stretch out the colors and increase the color contrast along the blue-yellow color continuum by our edits in the b channel. This is the strength of the LAB technique; it allows us to force colors apart which increases the dynamic impact of those colors.

Now, I picked 76 as a number that worked well for this image. For other images, you may want to move the slider more or less than what we did here.

Okay, it’s time to check out our results. This is our image saturated with the Hue/Saturation adjustment. Here is our image saturated in LAB. Personally, I think that this is rather impressive. Okay, we now have a nicely saturated image. So, are we done yet? Not yet. I have more that I would like to show you. However, to see what we’ve got next, you’ll need to watch Part II of this video series.