Luminar 2018 Feature of the Month: What is a Lookup Table (LUT) and how to use it?

What is a Lookup Table (LUT)?

The latest version of Luminar adds support for lookup tables or LUTs.  But what exactly does that mean to a creative photographer?  Turns out a LOT!  You can use a lookup table to change the appearance of your photo quickly.  

What is a LUT?

A Look Up Table, or LUT, is essentially a digital file that transforms the color and tone of your image.  It essential can convert colors and details in a source file to a new destination state.  For example, you can use a LUT to convert a modern digital photo to the color and tone of an older film stock.  Or perhaps to convert between a color image to an aged black and white treatment.

A LUT essentially transforms tone and color based upon settings chosen by the creator of the LUT. Each RGB combination of color has a new value assigned.  For example this particulate shade of violet has been remapped to a darker purple.

But they don’t just change one color value in an image… they change all.  

Why Use a LUT?

In this example, here’s a lookup table based upon an aged film stock from the early 1900’s. First let’s look at it applied to a color photo.  The image on the left are the original colors and on the right are the newly remapped.

You can see that the colors shift relatively dramatically as do tonal values.  Translating the LUT into a Curve looks a bit like this.

The Blue and Green channels of the image have been reduced and darkened, while the red channel has been more subtly shifted.  You can also see this if we view the LUT as a cube model.  The cube on the left is an unmodified image while the one on the right represent the changed RGB values.

Now, let’s look at the LUT when combined with a black and white adjustment.  In this case I converted the image to black and white, and then applied the LUT.  The split screen below makes it easy to see the three states.

As you can see, a lookup table is similar to a Curves adjustment, in that it can transform the color and tone.  Luminar includes the ability to apply LUTs to an image easily.

Using LUT Mapping

You’ll find a collection of built-in LUTs in Luminar 2018 as well as an option to load more. The included LUTs are meant to offer quick ways for film stocks, black and white looks, and creative color grades.  A LUT can be used to unlock a new style in seconds. 

1. Open an image in Luminar.

2. Choose a desired workspace to edit.  Many include LUT mapping in them.

3. If needed, click the Add Filters button.

4. Choose LUT Mapping from the professional category.

5. In the controls for the LUT Mapping effect, click the button labeled Choose LUT. 

 You’ll find several built-in stylize in the pop-up list, you can also load your own lookup tables in the .cube format.

6. Select a desired LUT from the list or choose Load Custom LUT File… to select a LUT in the .cube format.

7. Adjust the Amount, Contrast, and Saturation sliders to taste to stylize the image.

Amount. This lets you reduce the intensity of the Lookup Table.

Contrast. This impacts the overall contrast in the image and can be used to refine the LUT’s appearance.

Saturation. This impacts the overall saturation in the image and can also be used to refine the LUT’s appearance.

8. Continue editing the image as needed to get the desired look.

Advice for LUTs and Presets

For best results, choose a consistent place on your hard drive to store your LUT files.  For example your documents folder or perhaps a dropbox folder that syncs to all your computers.  This way you can always find any lookup tables you need.  Plus you can then store them as part off any custom presets you make. 

You can also try applying the LUT Mapping effect to an adjustment layer.  This makes it easy adjust the opacity and blending modes to unlock even more options.  We’ll be posting all sorts of recipes and tips to the blog all month.