What is a LUT?


Today’s Question: Can you explain, briefly, what LUTs are, a word I’ve been seeing lately. What can they do for still photographers beyond the garden-variety sliders in Photoshop, say, or the use of plug-ins? And do LUTs exist for black-and-white as well as color?

Tim’s Quick Answer: A “LUT” is a Lookup Table, which is used in several contexts to adjust the appearance of a display, or a photo or video. LUTs have become popular for providing what is similar to a preset for altering the appearance of a photo.

More Detail: For photographers, the earliest reference they might have heard to a “LUT” would have been in the context of color management. When calibrating and profiling a computer monitor display, the software will update the LUT on the graphics card, which in turn alters the behavior of the display. In other words, the LUT in this context determines how color and luminance data from the computer actually appears on the monitor display.

More recently, “LUT” has become something of a buzzword in the world of photo optimization. In video production LUTs have long been used as a tool for editing the appearance of video. For example, video is often captured with a very neutral appearance. A LUT can then be applied in post-processing to adjust the overall tonality and color appearance of the video. This is often referred to as “color grading”.

This concept has been adapted by many photographers to alter the appearance of their photos. The use of a LUT in this context is similar in concept to applying a preset to a photo, altering the appearance of photos in a uniform way, to achieve a particular look. This has led to the availability of LUTs to be used for this purpose, including options for both color and black and white interpretations of a photo.

In Photoshop, for example, you can apply a LUT to an image by going to the menu and choosing Image > Adjustments > Color Lookup. In the Color Lookup dialog, you can then select (or load) a LUT you would like to apply to the current image.