What is a LUT (lookup table)?

Think of it as an Instagram filter for professionals.

You know how futuristic movies always have that greyish-blue cast to everything? And how, when you watch something that’s supposed to take place in the 1970s, everything has a dark orange cast to it? When you’re watching reality shows, have you noticed that every time they’re showing you something that happened last week, the colors are a bit weaker?

All those things happen because of LUTs.

What a LUT is

LUT stands for “lookup table.” It’s a set of numbers that correspond to some serious math. When you take that LUT and apply it to a photo, the photo is changed in a way that makes things… feel different. LUTs can be subtle, or they can be very obvious.

Some of the first uses for LUTs were in the late 1990s. For about a decade, hit shows like Friends and Frasier were shot on film and edited on video. This was more expensive than shooting on video, but the result looked, well, a lit more serious. Shows shot on video tape seem a bit too well-lit, a bit too fake.

By applying a LUT to freshly-shot video, it could look like film. All the characteristics of film would transfer over. Or so that was the idea. Early LUTs simply made everything look dark and washed out. But the technology got better.

Regular folks became aware of LUTs in the late ’00s with apps like Hipstamatic and Instagram. It was easy to take a freshly shot photo and make it look like a Polaroid or hand-tinted portrait. You were using LUTs the whole time and you didn’t know it.

Examples of LUTs

I took this image from a marketing web site and added some standard color squares to the right of it to make the changes a little more obvious. The photo is the same, I just added a LUT to it to show you what could be done.

This is the original photo. It’s a bright, sunny day, and the fleshtones and greenery looks natural. Now look at this one:

 

Here I’ve applied a very subtle LUT that washes out the image a bit to make it look like a color print that you took a photo of. It’s not that different but you can see the colors are a little washed out and the fleshtones are a little redder.

 

This is the same photo with a filter to simulate Kodachrome film from the 1980s. The greens are very green. All the colors are a little unnatural. But it does look like less of a “studio” photo and more like something that someone took with their own camera and got developed at the Fotomat. It’s a happy photo, and it makes of think of happy times.

 

Finally, here’s the same photo, designed to look like someone in some post-apocalyptic desert landscape found it. Everything is faded back. It looks like it comes from long ago, from a time that we remember with a bit of sadness.

And folks, this is all the same photo.

If you really want to see what LUTs can do, check out the AMC series Kevin Can F Himself. This show toggles between looking like a traditional 1990s “yuckfest” and a modern dark comedy. Every time it changes, the look of the show changes from bright and saturated to dark and moody. I’m sure that to some degree the lighting and camera exposure change between the “sitcom” and “drama” scenes but I’m also sure a LUT is used to make the effect even more pronounced.

Why does someone reading this blog care about LUTs?

Because they’re all around you. Every movie made today is shot digitally, and a LUT is used to make it look “like a movie.” Every gritty TV show uses one. If you liked WandaVision, you probably dug the groovy “old TV show” vibes. A separate and different LUT simulated every one of those decades. Even the black and white shows used a LUT to make the greys look flat and weak like old TV screens.

If you like TV, and you like what you see, your experience is full of LUTs. Your TV may even have settings like “Cinema” or “Demo” or “Classic.” These basic LUTs come from the manufacturer designed to give you the best experience while watching.

But, it goes without saying, Solid Signal doesn’t sell them. And so, dear reader, I hope you do shop at Solid Signal for the many things that we do sell. They pay for informational articles like these.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.