What Is a LUT?
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A stock image composite using a pink and purple toning lut
Hi folks! I trust that you are all doing well. The topic of the use of LUTs for still photography waxes and wanes, but the idea of what a LUT is, is still not clear to many, so I thought it might be appropriate to explain what a LUT is, why you might want to use one and where you would do so.
Definition
LUT is an acronym for Look Up Table. LUTs are algorithms that take an input value related to colour and remaps that data based on the algorithm to deliver a different value. This is sometimes inferred to be like a preset, although such an understanding ignores the algorithm, as the results of applying a LUT are dependent on the input data. this is unlike a preset which just applies a fixed change.
Why LUTs
The idea of the LUT transformation was created for use in the editing of film and video projects with specific focus in the speciality of colour grading. LUTs historically were used to convey a mood or to propose an environment.
Some older examples that remain very illuminating are the initial episodes of two now long cancelled TV programs where the LUT application went badly out of control. Both programs were in the CSI franchise. In CSI Miami, a LUT was applied to the outdoor footage using what is often called the orange-teal model. Anything in the input stream that was a highlight had an orange tint applied and anything in the shadows had a teal tint applied. The orange was used to convey a mood of heat, or warm and humid temperatures. The teal was used in the shadows to create counterpoints of cool temperatures and based on where in the input stream water would fall to give it an appealing colour. The initial episodes were so overdone, that viewers were made uneasy and the editors made changes in short order to make the alterations look less unnatural.
Another example comes from the first episodes of CSI New York. The colourists task was to make New York appear to be a colder city, not so much in temperature but in attitude so a LUT was used to add a blue tint to everything. The first episodes were so blue that viewers were repulsed and again adjustments were made quickly to lower the intensity of the LUT in order to not drive viewers away.
These examples show that when using a LUT, in general, subtlety is your goal. Excessively strong LUTs can disengage an audience.
Why LUTs
An example where strong LUTs worked, is in The Matrix where everything happening in the matrix, particularly at the beginning when the matrix is not yet known is a green tint. Anything happening outside the matrix did not have the LUT applied making it easy for the viewer to subconsciously identify where the events on screen were unfolding. The colourist work was so effective that most viewers only noticed the LUT subliminally. This success of course resulted in LUTs being used regularly in television and particularly in advertising to make subliminal mood alterations.
LUTs are just mathematical transformations, but that doesn’t mean that they cannot be used in negative ways.
LUTs for Still Photography
As still cameras had powerful video capability added, some cameras were given the ability to apply a LUT in the recording process. This is a rather lazy method, but for those who want it, it can work. Professional colourists want as close to untouched footage as possible so they have the greatest latitude in editing, but most amateur videographers do not understand and do not want to get into colourist skills.
Adobe added a colourization model to Lightroom Classic that originated in their high end video editor Premiere Pro. It works well, although it is not LUT oriented, but adoption has been very limited, mostly due to a lack of interest and poor quality training materials.
LUTs were then made available as downloads for use in photo editors that can apply a LUT in post. These were more successful because they behaved like presets, in a fire and forget model, although some users became disenchanted because a series of different images did not all have the same look, because the LUT is based on the input data, rather than what some call a shot of paint.
Which Photo Editors Can Use LUTs?
While a LUT may seem to be like a preset, they are very different entities. Originally LUTs were simple files, but current LUTs are referred to as 3D LUTs. This, in a simplification, means a more advanced algorithm with greater levels of control. As noted earlier, LUTs were built for video, but there are some still editors that can use LUTs.
Adobe Photoshop
The editor most people think of first is Adobe Photoshop and this product can indeed use LUTs. After you obtain the LUT that you want to use (some are free, better ones are not) you have a file that ends in .cube, aka a Cube LUT or 3D LUT. In Photoshop create a Color Lookup Adjustment Layer, and then in the Properties choose 3D LUT
When you click on the down arrow, you will see LUTs that you have installed as well as some included with Photoshop.
If you have Photoshop, I encourage you to try this. LUTs tend to be far more subtle and less like a rattle can of spray paint than presets.
Adobe Lightroom Classic
Using LUTs in Lightroom Classic is a bit of a pain in the ass. Open the image that you want to use a LUT on in the Develop module. Now send the image to Photoshop from Lightroom. In Photoshop, from the Filter menu, choose Camera RAW Filter. In Adobe Camera RAW, hold down ALT or OPTION while clicking on the three dot icon in the right side stack and then click Create Preset. In the dialog, choose 3D LUT and then load the LUT .cube file that you want to use. Save this as a new preset.
Return to Lightroom Classic and open the Basic panel. In the Profiles area, click the four squares and scroll to the User Profiles section in the Profile Browser. The LUT preset that you have created is available to you there, and you will see a thumbnail of the effect that the LUT will provide if you apply it.
Both Capture One and Affinity Photo also support the use of LUTs. There are likely others, but these are the ones that I know and use.
Can I Create My Own LUT?
The answer is yes. High end video editors such as my preferred DaVinci Resolve provide this capability natively. There are also online services where you download a default file, make your adjustments to it and then upload it. The service then creates a LUT. You can even create a LUT from within Photoshop. I am skeptical about some of these incredibly simple tools, because I wonder about the validity of the algorithm given that they are based on single samples and single input streams, but you should do what you want.
Getting 3D LUTs Online
A quick search with your preferred search engine will reveal a ton of LUT providers. Some offer hundreds of options which inevitably invoke option paralysis. I do propose being selective in what you download and install. Sometimes LUTs are copyrighted and have a fee or usage restrictions but there are also a large number of LUTs created under the Creative Commons License that have no cost and no restrictions. Whatever route you choose, be sure to understand the licensing before use.
Wrap Up
As we see, LUTs are similar in the end to presets but are far more powerful and take into account the actual data in the image, something a preset cannot do. If you are a fan of presets, you may find it worth your while to invest some time in learning about LUTs, however, always remember that a LUT only alters an image. Applying a LUT does not fix an image that is already crap.
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