Correction in the Lab

We continue our acquaintance with image correction methods in the Lab color space. The lesson has a purely practical focus, so I will not give a detailed explanation on the topic: how and why this or that technique works. Those who wish to study the theoretical aspects and more complex methods I recommend to study the works of the famous guru in the field of color correction Dan Margulis.

And we will proceed to the lesson. After examining it, you will spend no more than 2-3 minutes on correcting such pictures, and if you do an action, then a few seconds.

Step 1

Open the image that we want to subject to correction. In this case, it is a landscape shot.

Analyze the image. As you can see, you need to increase the dynamic range of brightness, that is, to show more detail in the shadows and slightly darken the bright areas. Further, I would make the sky bluer, increased the color variations of water, the greens can also be made more juicy and diverse in shades. And the final step will be a two-step sharpening.

Since the photo was taken in bright sunlight, you can not worry about the amplification of color noise during color correction. However, in other cases it must be borne in mind. So, first of all duplicate the layer by clicking CTRL + J.

Step 2

We transfer our photo to the mode Lab. This is done by the command Image – Mode – Lab (Image – Mode – Lab).

Correction in the Lab

Select a duplicate layer. Then go to the palette Channels (Channels) and select channel brightness (Lightness).

Correction in the Lab

Then click on the channel eye. Lab, to see the image in color.

Correction in the Lab

I do this by pressing two key combinations. CTRL + 1 and ~, which is much faster. In the CS4 version, the key combinations will be different: CTRL + 3 and ~.

Step 3

Apply the command Image – Correction – Light / Shadows (Image – Adjustment – Shadows / Highlights). We didn’t accidentally choose Brightness channel in step 2. Now the command will be applied only to it, and since the information about color and contrast in the mode Lab located in different channels, we will avoid increasing the color noise and the appearance of color artifacts.
Settings in each case will be different, practice and quickly understand how and in what cases to do.

Correction in the Lab

Step 4

Now let’s do the color. Channels a and b in the Lab color model will be able to give us any number of colors, even one that cannot be displayed on the monitor and which does not exist in nature. Use the channel overlay method with the command External channel (Apply Image). Select the channel “but” in the channel palette, similarly to step 2. Go to the menu Image – External Channel (Image – Apply Image). Select the blend mode Overlap (Overlay) or Soft light (Soft Light).

Correction in the Lab

Step 5

Choosing a channel b and also impose it on itself in mode Overlap.
Do not forget that we can vary the value Transparency (Opacity) in the dialog box of this command. Here is the result after operations with channels.

Correction in the Lab

Note: you can also use the command Curves (Curves) and build curves “but” and b on control points. This method gives the broadest possibilities, but requires serious preparation.

Step 6

Do not worry about excessive saturation of colors. You just need to lower the opacity of the layer. I stopped at about thirty%, you may have a different meaning.

Step 7

Now we are committed to sharpening. We will do this in an unusual way, in two stages. In the first stage, the sharpness and contrast of large areas of the image increases, in the second, small details are worked out. First, let’s check in the channel palette whether we have the Brightness channel selected. Go to the menu Filter – Sharpness – Contour Sharpness (Filter – Sharpen – Unsharp mask). We move the sliders Effect (Amount) and Radius (Radius) right to the end. It turned out that, but it should be so.

Now, begin to reduce the values Radius until the appearance of clear transitions between relatively large objects, but avoiding the appearance of fine details.

Next, reduce the value Effect, almost always it will be less than the value used in the classical method.

That is why this method has the English abbreviation HIRALOAM (High Radius – Low Amount). Reaching the optimal value, we increase the value Threshold (Threshold) to exclude the action of the command on small parts.

Step 8

Increase the sharpness of the fine details of the image. Apply the same command Contour sharpness, but in the standard version.

And here is the final result.

Unfortunately, with this size of the picture it is difficult to assess the results of sharpening, but I assure you, they will please you. In the following lessons, we’ll continue our introduction to the Lab color space.

I wish you all creative success!

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